MedWorm.com provides a medical RSS filtering service. Over 6000 RSS medical sources are combined and output via different filters. This feed contains the latest items from the 'Chromosoma' source. Fri, 19 Mar 2010 17:00:25 +0100 http://www.medworm.com/index.php?rid=3377274&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fvmg2736228237r33%2F Abstract  During mitosis, all chromosomes must attach to microtubules of the mitotic spindle to ensure correct chromosome segregation. Microtubule attachment occurs at specialized structures at the centromeric region of chromosomes, called kinetochores. These kinetochores can generate microtubule attachments through capture of centrosome-derived microtubules, but in addition, they can generate microtubules themselves, which are subsequently integrated with centrosome-derived microtubules to form the mitotic spindle. Here, we have performed a large scale RNAi screen and identify cyclin G-associated kinase (GAK) as a novel regulator of microtubule generation at kinetochores/chromatin. This function of GAK requires its C-terminal J-domain, which is essential for clathrin recyc... Chromosoma journals http://www.medworm.com/rss/comments.php?id=3377274 Tue, 16 Mar 2010 14:49:18 +0100 3377274 http://www.medworm.com/index.php?rid=3361722&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F2027175265xw3212%2F Abstract  Although nucleosome remodeling is essential to transcriptional regulation in eukaryotes, little is known about its genome-wide behavior. Since a number of nucleosome positioning maps in vivo have been recently determined, we examined if their comparisons might be used for obtaining a genome-wide profile of nucleosome remodeling. Using seven yeast maps, the local variability of nucleosomes, measured by the entropy, was significantly higher in a set of reported unstable nucleosomes. The binding sites of four transcription factors, known as the remodeling factors, were distinctively high both in entropy and linker ratio, whereas those of Yhp1, their potential inhibitor, showed the lowest values in both of them. Taken together, our map shows the general information of... Chromosoma journals http://www.medworm.com/rss/comments.php?id=3361722 Thu, 11 Mar 2010 18:12:23 +0100 3361722 http://www.medworm.com/index.php?rid=3361721&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fa5401p23382128l8%2F Abstract  The chromatin structure is important for recognition and repair of DNA damage. Many DNA damage response proteins accumulate in large chromatin domains flanking sites of DNA double-strand breaks. The assembly of these structures—usually termed DNA damage foci—is primarily regulated by MDC1, a large nuclear mediator/adaptor protein that is composed of several distinct structural and functional domains. Here, we are summarizing the latest discoveries about the mechanisms by which MDC1 mediates DNA damage foci formation, and we are reviewing the considerable efforts taken to understand the functional implication of these structures. Content Type Journal ArticleCategory REVIEWDOI 10.1007/s00412-010-0266-9Authors Stephanie Jungmichel, University of Zürich Ins... Chromosoma journals http://www.medworm.com/rss/comments.php?id=3361721 Thu, 11 Mar 2010 18:12:23 +0100 3361721 http://www.medworm.com/index.php?rid=3357684&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fb2226p287h1u3649%2F Abstract  In the zebra finch (Taeniopygia guttata) a germline-restricted chromosome (GRC) is regularly present in males and females. While the GRC is euchromatic in oocytes, in spermatocytes this chromosome is cytologically seen as entirely heterochromatic and presumably inactive. At the end of male meiosis, the GRC is eliminated from the nucleus. By immunofluorescence on microspreads, we investigated HP1 proteins and histone modifications throughout male meiotic prophase, as well as in young spermatid stages after the GRC elimination. We found that in prophase spermatocytes the GRC chromatin differs from that of the regular chromosome complement. The GRC is highly enriched in HP1β and exhibits high levels of di- and tri-methylated histone H3 at lysine 9 and tri- and di-met... Chromosoma journals http://www.medworm.com/rss/comments.php?id=3357684 Wed, 10 Mar 2010 16:14:36 +0100 3357684 http://www.medworm.com/index.php?rid=3325897&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fl33784853329h121%2F Abstract  Over the last several years, the sea lamprey (Petromyzon marinus) has grown substantially as a model for understanding the evolutionary fundaments and capacity of vertebrate developmental and genome biology. Recent work on the lamprey genome has resulted in a preliminary assembly of the lamprey genome and led to the realization that nearly all somatic cell lineages undergo extensive programmed rearrangements. Here we describe the development of a bacterial artificial chromosome (BAC) resource for lamprey germline DNA and use sequence information from this resource to probe the subchromosomal structure of the lamprey genome. The arrayed germline BAC library represents ∼10× coverage of the lamprey genome. Analyses of BAC-end sequences reveal that the lamprey genom... Chromosoma journals http://www.medworm.com/rss/comments.php?id=3325897 Mon, 01 Mar 2010 18:07:55 +0100 3325897 http://www.medworm.com/index.php?rid=3297494&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Ffh784k0828h732j7%2F Abstract  More than 109 base pairs of the genome in higher eucaryotes are positioned in the interphase nucleus such that gene activation, gene repression, remote gene regulation by enhancer elements, and reading as well as adjusting epigenetic marks are possible. One important structural and functional component of chromatin organization is the zinc finger factor CTCF. Two decades of research has advanced the understanding of the fundamental role that CTCF plays in regulating such a vast expanse of DNA. Content Type Journal ArticleCategory REVIEWDOI 10.1007/s00412-010-0262-0Authors Rolf Ohlsson, Karolinska Institute Institute for Microbiology, Tumor- and Cellbiology (MTC) Stockholm SwedenMarek Bartkuhn, Justus-Liebig-University Institute for Genetics 35392 Giessen Germa... Chromosoma journals http://www.medworm.com/rss/comments.php?id=3297494 Sat, 20 Feb 2010 06:50:17 +0100 3297494 http://www.medworm.com/index.php?rid=3282717&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fe11532x5101k5301%2F Abstract  During male meiotic prophase in mammals, X and Y are in a largely unsynapsed configuration, which is thought to trigger meiotic sex chromosome inactivation (MSCI). In avian species, females are ZW, and males ZZ. Although Z and W in chicken oocytes show complete, largely heterologous synapsis, they too undergo MSCI, albeit only transiently. The W chromosome is already inactive in early meiotic prophase, and inactive chromatin marks may spread on to the Z upon synapsis. Mammalian MSCI is considered as a specialised form of the general meiotic silencing mechanism, named meiotic silencing of unsynapsed chromatin (MSUC). Herein, we studied the avian form of MSUC, by analysing the behaviour of the peculiar germline restricted chromosome (GRC) that is present as a single... Chromosoma journals http://www.medworm.com/rss/comments.php?id=3282717 Tue, 16 Feb 2010 18:06:04 +0100 3282717 http://www.medworm.com/index.php?rid=3282718&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F5230476172434271%2F Abstract  The spindle checkpoint restrains anaphase onset and mitotic exit until all chromosomes are stably attached to the mitotic spindle via their kinetochores. The Tao1 protein kinase was recently reported as a novel spindle checkpoint component. When an siRNA was used to repress Tao1, the essential spindle checkpoint component Mad2 failed to localise to kinetochores, and cells rapidly exited mitosis. Tao1 was also shown to interact with BubR1, another essential checkpoint component, and be rapidly degraded after mitosis, a feature typical of many mitotic regulators. Here, we identify four different siRNAs that repress Tao1 protein levels as efficiently as the previously reported siRNA. However, these siRNAs do not override the spindle checkpoint. We also present data i... Chromosoma journals http://www.medworm.com/rss/comments.php?id=3282718 Tue, 16 Feb 2010 18:06:00 +0100 3282718 http://www.medworm.com/index.php?rid=3270859&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Ffh0hr11587231u62%2F Abstract  Two partially reconstructed karyotypes (RK1 and RK2) of Arabidopsis thaliana have been established from a transformant, in which four structurally changed chromosomes (α, β, γ, and δ) were involved. Both karyotypes are composed of 12 chromosomes, 2n = 1¢¢+ 3¢¢+ 4¢¢+ 5¢¢+ a¢¢+ g¢¢ = 12 for RK1 and 2n = 3¢¢+ 4¢¢+ 5¢¢+ a¢¢+ b¢¢+ g¢¢ = 12 for RK2, and these chromosome constitutions were relatively stable at least for three generations. Pairing at meiosis was limited to the homologues (1, 3, 4, 5, α, β, or γ), and no pairing occurred among non-homologous chromosomes in both karyotypes. For minichromosome α (mini α), precocious separation at metaphase I was frequently observed in RK2, as found for other minichromosomes, but was rare... Chromosoma journals http://www.medworm.com/rss/comments.php?id=3270859 Fri, 12 Feb 2010 07:08:13 +0100 3270859 http://www.medworm.com/index.php?rid=3242721&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F6177u43k8ju14384%2F Abstract  Eukaryotic genomes function in the context of chromatin, but the roles of most nonhistone chromosomal proteins are far from understood. The D1 protein of Drosophila is an example of a chromosomal protein that has been fairly well characterized biochemically, but has nevertheless eluded functional description. To this end, we have undertaken a gain-of-function genetical analysis of D1, utilizing the GAL4-UAS system. We determined that ubiquitous overexpression of D1 using the Act5C- or tubP-GAL4 drivers was lethal to the organism during larval growth. We also ectopically expressed D1 in a tissue-limited manner using other GAL4 drivers. In general, ectopic D1 was observed to inhibit differentiation and/or development. We observed effects on pattern formation of the adu... Chromosoma journals http://www.medworm.com/rss/comments.php?id=3242721 Tue, 02 Feb 2010 17:47:25 +0100 3242721 http://www.medworm.com/index.php?rid=3234639&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fv6k43684v660844q%2F Abstract  Cotton is a model system for studying polyploidization, genomic organization, and genome-size variation because the allotetraploid was formed 1-2 million years ago, which is old enough for sequence divergence but relatively recent to maintain genome stability. In spite of characterizing random genomic sequences in many polyploidy plants, the cytogenetic and sequence data that decipher homoeologous chromosomes are very limited in allopolyploid species. Here, we reported comprehensive analyses of integrated cytogenetic and linkage maps of homoeologous chromosomes 12A and 12D in allotetraploid cotton using fluorescence in situ hybridization and a large number of bacterial artificial chromosomes that were anchored by simple sequence repeat markers in the correspon... Chromosoma journals http://www.medworm.com/rss/comments.php?id=3234639 Mon, 01 Feb 2010 18:02:39 +0100 3234639 http://www.medworm.com/index.php?rid=3234640&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F4rr027r13010j5p1%2F Abstract  Unreductional meiotic cell division (UMCD) generates unreduced gametes and leads to polyploidy. The tetraploid wheat “Langdon” (LDN) undergoes normal meiosis, but its polyhaploid undergoes UMCD. Here, we found that sister kinetochores oriented syntelically at meiosis I in LDN, but amphitelically in LDN polyhaploid and the interspecific hybrid of LDN with Aegilops tauschii. We also observed that sister centromere cohesion persisted until anaphase II in LDN, LDN polyhaploid, and the interspecific hybrid. Meiocytes with all chromosomes oriented amphitelically underwent UMCD in LDN polyhaploid, and the interspecific hybrid, suggesting the tension created by the amphitelic orientation of sister kinetochores and persistence of centromeric cohesion between sister chro... Chromosoma journals http://www.medworm.com/rss/comments.php?id=3234640 Mon, 01 Feb 2010 18:02:37 +0100 3234640 http://www.medworm.com/index.php?rid=3207491&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fe52604v313vr74w5%2F Abstract  Calpains form a family of Ca2+-dependent cysteine proteases involved in diverse cellular processes. However, the specific functions of each calpain isoform remain unknown. Recent reports have shown that calpain 2 (Capn2) is essential for cell viability. We have recently shown that Capn2 is a nuclear protease associated with chromosomes during mitosis in mammalian embryonic cells. We now report that Capn2 depletion impairs mitosis and induces apoptosis in murine cells. Low Capn2 levels induce chromosome alignment defects, the loss of histone H3 threonine 3 phosphorylation at centromeres, and premature sister chromatid separation. Thus, Capn2 may play a role in fundamental mitotic functions, such as the maintenance of sister chromatid cohesion. Content Type Journa... Chromosoma journals http://www.medworm.com/rss/comments.php?id=3207491 Fri, 22 Jan 2010 10:08:52 +0100 3207491 http://www.medworm.com/index.php?rid=3192550&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fj38668616n8207p7%2F Abstract  Chromatin insulators affect interactions between promoters and enhancers/silencers and function as barriers to the spread of repressive chromatin. Recently, we have found an insulator, named Wari, located on the 3′ side of the white gene. Here, we show that the previously identified 368-bp core of this insulator is sufficient for blocking Polycomb response element-mediated silencing. Although Wari does not contain binding sites for known insulator proteins, the E(y)2 and CP190 proteins bind to Wari as well as to the Su(Hw)-containing insulators in vivo. It may well be that these proteins are recruited to the insulator by as yet unidentified DNA-binding protein. Partial inactivation of E(y)2 in a weak e(y)2 u1 mutation impairs only the anti-silencing but not t... Chromosoma journals http://www.medworm.com/rss/comments.php?id=3192550 Fri, 15 Jan 2010 17:59:09 +0100 3192550 http://www.medworm.com/index.php?rid=3121852&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F03353h53h300j70k%2F Abstract  Heterochromatin protein 1 (HP1), which binds to sites of histone H3 lysine 9 (H3K9) methylation, is primarily responsible for gene silencing and the formation of heterochromatin. We observed that HP1β is located in both the chromocenters and fibrillarin-positive nucleoli interiors. However, HP1α and HP1γ occupied fibrillarin-positive compartments to a lesser extent, corresponding to the distinct levels of HP1 subtypes at the promoter of rDNA genes. Deficiency of histone methyltransferases SUV39h and/or inhibition of histone deacetylases (HDACi) decreased HP1β and H3K9 trimethylation at chromocenters, but not in fibrillarin-positive regions that co-localized with RNA polymerase I. Similarly, SUV39h- and HDACi-dependent nucleolar rearrangement and inhibition of ... Chromosoma journals http://www.medworm.com/rss/comments.php?id=3121852 Wed, 23 Dec 2009 22:22:23 +0100 3121852 http://www.medworm.com/index.php?rid=3121853&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fpg52448206047278%2F Abstract  Chromatin insulators are required for proper temporal and spatial expression of genes in metazoans. Here, we have analyzed the distribution of insulator proteins on the 56F–58A region of chromosome 2R in Drosophila polytene chromosomes to assess the role of chromatin insulators in shaping genome architecture. Data show that the suppressor of Hairy-wing protein [Su(Hw)] is found in three structures differentially associated with insulator proteins: bands, interbands, and multi-gene domains of coexpressed genes. Results show that bands are generally formed by condensation of chromatin that belongs to genes containing one or more Su(Hw) binding sites, whereas, in interbands, Su(Hw) sites appear associated with open chromatin. In addition, clusters of coexpressed gen... Chromosoma journals http://www.medworm.com/rss/comments.php?id=3121853 Wed, 23 Dec 2009 22:22:21 +0100 3121853 http://www.medworm.com/index.php?rid=3106551&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F544q5163q5r273h5%2F Abstract  In addition to the standard set of chromosomes (A), about 15% of eukaryote genomes carry B chromosomes. In most cases, B chromosomes behave as genomic parasites being detrimental for the individuals carrying them and prospering in natural populations because of transmission advantages (drive). B chromosomes are mostly made up of repetitive DNA sequences, especially ribosomal DNA (rDNA), satellite DNA and mobile elements. In only two cases have B chromosomes been shown to carry protein-coding genes. Although some B chromosomes seem to have derived from interspecific hybridisation, the most likely source of B chromosomes is the host genome itself, but the specific A chromosome being the B ancestor has not been identified in any B-containing species. Here, we provide... Chromosoma journals http://www.medworm.com/rss/comments.php?id=3106551 Thu, 17 Dec 2009 07:03:37 +0100 3106551 http://www.medworm.com/index.php?rid=3081662&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F9237h35814334452%2F Abstract  NMCP1 is a plant protein that has a long coiled-coil domain within the molecule. Newly identified NMCP2 of Daucus carota and Apium graveolens showed similar peripheral localization in the interphase nucleus, and the sequence spanning the coiled-coil domain exhibited significant similarity with the corresponding region of NMCP1. To better understand disassembly and assembly of the nuclear envelope (NE) during mitosis, subcellular distribution of NMCP1 and NMCP2 was examined using A. graveolens cells. AgNMCP1 (NMCP1 in Apium) disassembled at prometaphase, dispersed mainly within the spindle, and accumulated on segregating chromosomes, while AgNMCP2 (NMCP2 in Apium), following disassembly at prometaphase with timing similar to that of AgNMCP1, dispersed throughout the m... Chromosoma journals http://www.medworm.com/rss/comments.php?id=3081662 Tue, 08 Dec 2009 19:47:22 +0100 3081662 http://www.medworm.com/index.php?rid=3078163&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fbr7163xw8q320125%2F Abstract  The haspins are divergent members of the eukaryotic protein kinase family that are conserved in many eukaryotic lineages including animals, fungi, and plants. Recently-solved crystal structures confirm that the kinase domain of human haspin has unusual structural features that stabilize a catalytically active conformation and create a distinctive substrate binding site. Haspin localizes predominantly to chromosomes and phosphorylates histone H3 at threonine-3 during mitosis, particularly at inner centromeres. This suggests that haspin directly regulates chromosome behavior by modifying histones, although it is likely that additional substrates will be identified in the future. Depletion of haspin by RNA interference in human cell lines causes premature loss of cen... Chromosoma journals http://www.medworm.com/rss/comments.php?id=3078163 Tue, 08 Dec 2009 06:45:21 +0100 3078163 http://www.medworm.com/index.php?rid=3078164&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F4776p64k6p3k62u0%2F Abstract  Cajal bodies (CBs) are subnuclear domains that participate in spliceosomal small nuclear ribonucleoprotein (snRNP) biogenesis and play a part in the assembly of the spliceosomal complex. The CB marker protein, coilin, interacts with survival of motor neuron (SMN) and Sm proteins. Several coilin phosphoresidues have been identified by mass spectrometric analysis. Phosphorylation of coilin affects its self-interaction and localization in the nucleus. We hypothesize that coilin phosphorylation also impacts its binding to SMN and Sm proteins. In vitro binding studies with a C-terminal fragment of coilin and corresponding phosphomimics show that SMN binds preferentially to dephosphorylated analogs and that SmB′ binds preferentially to phosphomimetic constructs. Bacte... Chromosoma journals http://www.medworm.com/rss/comments.php?id=3078164 Mon, 07 Dec 2009 19:35:24 +0100 3078164 http://www.medworm.com/index.php?rid=3055408&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F6h60564544758766%2F Abstract  The MYST histone acetyltransferase (HAT) dTip60 is part of a multimeric protein complex that unites both HAT and chromatin remodeling activities. Here, we sought to gain insight into the biological functions of dTip60. Strong ubiquitous dTip60 knock-down in flies was lethal, whereas knock-down in the wing imaginal disk led to developmental defects in the wing. dTip60 localized to the nucleus in early embryos and was present in a large number of interbands on polytene chromosomes. Genome-wide expression analysis upon depletion of dTip60 in cell culture showed that it regulated a large number of genes in Drosophila, among which those with chromatin-related functions were highly enriched. Surprisingly, a significant portion of these genes were upregulated upon dTip60 ... Chromosoma journals http://www.medworm.com/rss/comments.php?id=3055408 Tue, 01 Dec 2009 08:30:00 +0100 3055408 http://www.medworm.com/index.php?rid=2987910&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fv9821150lk023723%2F Abstract  Chromosomal and telomeric reprogramming was assessed in intraspecies hybrids obtained by fusion of embryonic stem (ES) cells and mouse embryonic fibroblasts. Evaluation of the ploidy of ES-somatic hybrids revealed that 21 of 59 clones had a tetraploid DNA profile while the remaining clones showed deviations from the expected profile of fusion between two diploid cells. Microsatellite polymerase chain reaction analysis of four of these clones demonstrated no random loss of somatic chromosome pairs in the ES-somatic cell hybrids. Pluripotential of ES-somatic hybrids was assessed by gene expression analysis, antibody staining for Oct4 and SSEA-1 and teratoma formation containing derivatives of the three germ layers. Reprogramming of telomeric maintenance was observed... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2987910 Wed, 11 Nov 2009 07:05:39 +0100 2987910 http://www.medworm.com/index.php?rid=2987911&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F292xl556r480671m%2F Abstract  The DNA-dependent adenosine triphosphatase (ATPase) Plk1-interacting checkpoint helicase (PICH) has recently been implicated in spindle checkpoint (SAC) signaling (Baumann et al., Cell 128(1):101–114, 2007). Depletion of PICH by siRNA abolished the SAC and resulted in an apparently selective loss of Mad2 from kinetochores, suggesting a role for PICH in the regulation of the Mad1–Mad2 interaction. An apparent rescue of SAC functionality by overexpression of PICH in PICH-depleted cells initially seemed to confirm a role for PICH in the SAC. However, we have subsequently discovered that all PICH-directed siRNA oligonucleotides that abolish the SAC also reduce Mad2 mRNA and protein expression. This reduction is functionally significant, as PICH siRNA does not aboli... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2987911 Tue, 10 Nov 2009 18:45:07 +0100 2987911 http://www.medworm.com/index.php?rid=2937818&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fdh2jqp2t2886r2p3%2F Abstract  In all living cells, DNA is constantly threatened by both endogenous and exogenous agents. In order to protect genetic information, all cells have developed a sophisticated network of proteins, which constantly monitor genomic integrity. This network, termed the DNA damage response, senses and signals the presence of DNA damage to effect numerous biological responses, including DNA repair, transient cell cycle arrests (“checkpoints”) and apoptosis. The MRN complex (MRX in yeast), composed of Mre11, Rad50 and Nbs1 (Xrs2), is a key component of the immediate early response to DNA damage, involved in a cross-talk between the repair and checkpoint machinery. Using its ability to bind DNA ends, it is ideally placed to sense and signal the presence of double strand ... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2937818 Tue, 27 Oct 2009 17:59:31 +0100 2937818 http://www.medworm.com/index.php?rid=2881042&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F3247744j7403937x%2F Abstract  The synaptonemal complex (SC) is the central key structure for meiosis in organisms undergoing sexual reproduction. During meiotic prophase I, homologous chromosomes exchange genetic information at the time they are attached to the lateral elements by specific DNA sequences. Most of these sequences, so far identified, consist of repeat DNA, which are subject to chromatin structural changes during meiotic prophase I. In this work, we addressed the effect of altering the chromatin structure of repeat DNA sequences mediating anchorage to the lateral elements of the SC. Administration of the histone deacetylase inhibitor trichostatin A into live rats caused death of cells in the pachytene stage as well as changes in histone marks along the synaptonemal complex. The mo... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2881042 Fri, 09 Oct 2009 06:06:50 +0100 2881042 http://www.medworm.com/index.php?rid=2812009&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fal81823nq251v365%2F Abstract  In the fission yeast, Schizosaccharomyces pombe, synaptonemal complexes (SCs) are not formed during meiotic prophase. However, structures resembling the axial elements of SCs, the so-called linear elements (LinEs) appear. By in situ immunostaining, we found Pmt3 (S. pombe's SUMO protein) transiently along LinEs, suggesting that SUMOylation of some component(s) of LinEs occurs during meiosis. Mutation of the SUMO ligase Pli1 caused aberrant LinE formation and reduced genetic recombination indicating a role for SUMOylation of LinEs for the regulation of meiotic recombination. Western blot analysis of TAP-tagged Rec10 demonstrated that there is a Pli1-dependent posttranslational modification of this protein, which is a major LinE component and a distant homolog of the... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2812009 Wed, 16 Sep 2009 18:49:44 +0100 2812009 http://www.medworm.com/index.php?rid=2812008&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fa202pn7t3203206k%2F Abstract  Knowledge about the composition and structure of centromeres is critical for understanding how centromeres perform their functional roles. Here, we report the sequences of one centromere-associated bacterial artificial chromosome clone from a Coix lacryma-jobi library. Two Ty3/gypsy-class retrotransposons, centromeric retrotransposon of C. lacryma-jobi (CRC) and peri-centromeric retrotransposon of C. lacryma-jobi, and a (peri)centromere-specific tandem repeat with a unit length of 153 bp were identified. The CRC is highly homologous to centromere-specific retrotransposons reported in grass species. An 80-bp DNA region in the 153-bp satellite repeat was found to be conserved to centromeric satellite repeats from maize, rice, and pearl millet. Fluorescence in situ... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2812008 Wed, 16 Sep 2009 18:49:44 +0100 2812008 http://www.medworm.com/index.php?rid=2812010&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fr543qu673n481810%2F Abstract  Dnmt2 is a member of the animal DNA methyltransferase family of enzymes. While the role of other Dnmt proteins has been extensively characterized, comparably little is known about Dnmt2. This is surprising because Dnmt2 is the most widely conserved Dnmt protein, with homologues in protists, plants, fungi, and animals. In this review, we discuss the evidence supporting the seemingly contradictory roles of Dnmt2 in both DNA and RNA methylation. New studies are uncovering the enzymatic mechanisms that mediate these activities and also provide first insights into the biological functions of Dnmt2. Lastly, we also discuss observations that suggest a possible role for Dnmt2 in human health and disease, which further emphasizes the importance of defining Dnmt2-modulated ... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2812010 Wed, 16 Sep 2009 18:49:42 +0100 2812010 http://www.medworm.com/index.php?rid=2768095&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F9685562762225472%2F Abstract  The DNA of living cells is highly compacted. Inherent in this spatial constraint is the need for cells to organize individual genetic loci so as to facilitate orderly retrieval of information. Complex genetic regulatory mechanisms are crucial to all organisms, and it is becoming increasingly evident that spatial organization of genes is one very important mode of regulation for many groups of genes. In eukaryotic nuclei, it appears not only that DNA is organized in three-dimensional space but also that this organization is dynamic and interactive with the transcriptional state of the genes. Spatial organization occurs throughout evolution and with genes transcribed by all classes of RNA polymerases in all eukaryotic nuclei, from yeast to human. There is an increas... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2768095 Thu, 03 Sep 2009 06:25:27 +0100 2768095 http://www.medworm.com/index.php?rid=2745359&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F3n4p23v47025p7n4%2F Abstract  The retinoblastoma (pRb) family of proteins are well known for their tumor suppressor properties and for their ability to regulate transcription. The action of pRb family members correlates with the appearance of repressive chromatin marks at promoter regions of genes encoding key regulators of cell proliferation. Recent studies raise the possibility that pRb family members do not simply act by controlling the activity of individual promoters but that they may also function by promoting the more general organization of chromatin. In several contexts, pRb family members stimulate the compaction or condensation of chromatin and promote the formation of heterochromatin. In this review, we summarize studies that link pRb family members to the condensation or compactio... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2745359 Fri, 28 Aug 2009 16:58:44 +0100 2745359 http://www.medworm.com/index.php?rid=2736853&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Ft02h80wv134g2507%2F Abstract  Upon DNA double-strand break (DSB) induction in mammals, the histone H2A variant, H2AX, becomes rapidly phosphorylated at serine 139. This modified form, termed γ-H2AX, is easily identified with antibodies and serves as a sensitive indicator of DNA DSB formation. This review focuses on the potential clinical applications of γ-H2AX detection in cancer and in response to other cellular stresses. In addition, the role of H2AX in homeostasis and disease will be discussed. Recent work indicates that γ-H2AX detection may become a powerful tool for monitoring genotoxic events associated with cancer development and tumor progression. Content Type Journal ArticleCategory Mini-ReviewDOI 10.1007/s00412-009-0234-4Authors Jennifer S. Dickey, National Institutes of Healt... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2736853 Tue, 25 Aug 2009 16:45:57 +0100 2736853 http://www.medworm.com/index.php?rid=2736854&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fr0gw044155823242%2F Abstract  We have characterized two post-translational histone modifications in Caenorhabditis elegans on a genomic scale. Micrococcal nuclease digestion and immunoprecipitation were used to obtain distinct populations of single nucleosome cores, which were analyzed using massively parallel DNA sequencing to obtain positional and coverage maps. Two methylated histone H3 populations were chosen for comparison: H3K4 histone methylation (associated with active chromosomal regions) and H3K9 histone methylation (associated with inactivity). From analysis of the sequence data, we found nucleosome cores with these modifications to be enriched in two distinct partitions of the genome; H3K4 methylation was particularly prevalent in promoter regions of widely expressed genes, while H3... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2736854 Tue, 25 Aug 2009 06:54:16 +0100 2736854 http://www.medworm.com/index.php?rid=2729138&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fj46764538m277885%2F Abstract  Regulation of chromatin activity by covalent histone modifications has been long recognized. Histones that constitute the nucleosome are encoded by large families of genes and display a strong degree of conservation. However, histone variants exist and it is becoming clear that they play important roles in genome regulation. While most studies of the role of histone3 (H3) variants in transcriptional control comes from animal models, emerging data in plants suggest functional conservation, although plant-specific roles are likely. We review these data and speculate on the biological significance of H3 variants in plants. Content Type Journal ArticleCategory ReviewDOI 10.1007/s00412-009-0237-1Authors Mathieu Ingouff, National University of Singapore Department of... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2729138 Sun, 23 Aug 2009 05:45:05 +0100 2729138 http://www.medworm.com/index.php?rid=2718756&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fm01576p4205327jh%2F Abstract  Almost half of the human genome consists of repetitive DNA. Understanding what role these elements have in setting up chromatin states that underlie gene and chromosome function in complex genomes is paramount. The function of some types of repetitive DNA is obvious by virtue of their location, such as the alphoid arrays that define active centromeres. However, there are many other types of repetitive DNA whose evolutionary origins and current roles in genome biology remain unknown. One type of repetitive DNA that falls into this class is the macrosatellites. The relevance of these sequences to disease is clearly demonstrated by the 4q macrosatellite (D4Z4), whereupon contraction in the size of the array is associated with the onset of facioscapulohumeral muscular... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2718756 Wed, 19 Aug 2009 08:29:23 +0100 2718756 http://www.medworm.com/index.php?rid=2707989&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fqt0022g4k1pw3580%2F Abstract  In Drosophila polytene chromosomes, regions of intercalary heterochromatin are scattered throughout the euchromatic arms. Here, we present data on the first fine analysis of the individual intercalary heterochromatin region, 75C1-2, located in the 3L chromosome. By using electron microscopy, we demonstrated that this region appears as three closely adjacent condensed bands. Mapping of the region on the physical map by means of the chromosomal rearrangements with known breakpoints showed that the length of the region is about 445 kb. Although it seems that the SUUR protein binds to the whole 75C1-2 region, the proximal part of the region is fully polytenized, so the DNA underreplication zone is asymmetric and located in the distal half of the region. Finally, ... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2707989 Fri, 14 Aug 2009 17:47:29 +0100 2707989 http://www.medworm.com/index.php?rid=2666400&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fc98701v66m148834%2F Abstract  Eukaryotic genomes are highly organized within the cell nucleus. Genome organization not only implies the preferential positioning of genetic elements in the interphase nucleus but also the topographic distribution of biological processes. We have investigated the relationship between spatial organization and genome function in single cells. Myc, c-Met, Igf2r, Asb4, and Zac1 genes have the same radial distribution, but they are not positioned in close proximity with respect to each other. Three-dimensional mapping of their transcription sites uncovered a gene-specific pattern of relative positioning with respect to the nucleolus. We found that the Zac1 gene transcription preferentially occurs juxtaposed to the nucleolus, and that its mRNA accumulates at this site of... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2666400 Fri, 31 Jul 2009 19:47:56 +0100 2666400 http://www.medworm.com/index.php?rid=2662229&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fp352u36226606013%2F Abstract  Aneuploidy, which leads to unpaired chromosomal axes during meiosis, is frequently accompanied by infertility. We previously showed, using three mouse models of Down syndrome, that it is an extra chromosome, but not extra gene dose, that is associated with male infertility and virtual absence of post-meiotic gem cells. Here, we test the hypothesis that aneuploid segments are differentially modified and expressed during meiosis, depending on whether they are present as an extra chromosome or not. In all three models examined, the trisomic region lacks a pairing partner, but in one case, spermatocytes have an extra (and unpaired) chromosome, while the two other models involve translocation of the trisomic region rather than an extra chromosome. An extra unpaired chr... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2662229 Wed, 29 Jul 2009 07:16:43 +0100 2662229 http://www.medworm.com/index.php?rid=2652699&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fv6160m011n872746%2F We report here that egg cells of aged females show larger amounts of HP1 and Su(Var)3–9 than egg cells of young females. These data suggest that a determinant of sex may be the amount of maternally derived heterochromatic proteins. Content Type Journal ArticleCategory Research ArticleDOI 10.1007/s00412-009-0231-7Authors Giovanni Luigi Buglia, University of Rome “La Sapienza” Department of Genetics and Molecular Biology P.le A. Moro 5 00185 Rome ItalyDaniela Dionisi, University of Rome “La Sapienza” Department of Genetics and Molecular Biology P.le A. Moro 5 00185 Rome ItalyMarina Ferraro, University of Rome “La Sapienza” Department of Genetics and Molecular Biology P.le A. Moro 5 00185 Rome Italy Journal ChromosomaOnline ISSN 1432-0886Print ISSN 0009-5915 (Sourc... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2652699 Mon, 27 Jul 2009 21:50:09 +0100 2652699 http://www.medworm.com/index.php?rid=2639411&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F471w7u712158n627%2F Abstract  In budding yeast, we have found that sister rDNA arrays marked with fluorescent probes can be visualized as two distinguishable strands during metaphase. Upon anaphase, these arm loci are drawn into the spindle, where they adopt a cruciform-like structure and stretch 2.5-fold as they migrate to the poles. Therefore, while sister rDNA arrays appear separated in metaphase, mechanical linkages between sister arm loci persist throughout anaphase in yeast, as shown in grasshopper spermatocytes (Paliulis and Nicklas 2004). These linkages are partially dependent on the protector of cohesin, SGO1. In anaphase, the spatially regulated dissolution of these mechanical linkages serves to prevent premature sister separation and restrain the rate of spindle elongation. Thus, si... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2639411 Thu, 23 Jul 2009 09:00:33 +0100 2639411 http://www.medworm.com/index.php?rid=2633263&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fq35447735r324251%2F Abstract  The cell cycle-associated phosphorylation of histone H1.5 is manifested as three discrete phosphorylated forms, occurring exclusively on Ser17, Ser172, and Ser188 during interphase. During late G2 and mitosis the up-phosphorylation occurs exclusively on threonine at either Thr137 or Thr154 to build the tetraphosphorylated forms of H1.5, whereas the pentaphosphorylated forms result from phosphorylation at Thr10. To determine the kinetic and spatial distribution of histone H1 phosphorylation within the nucleus of synchronized Hela cells we localized three distinct phosphorylation sites of histone subtype H1.5 using affinity-purified polyclonal antibodies generated against phosphorylated Ser17, Ser172, and Thr10. Immunofluorescence labeling of synchronized HeLa cells us... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2633263 Sat, 18 Jul 2009 08:27:33 +0100 2633263 http://www.medworm.com/index.php?rid=2592847&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fq4kx184v53774748%2F Abstract  Centromeres, the chromosomal loci that form the sites of attachment for spindle microtubules during mitosis, are identified by a unique chromatin structure generated by nucleosomes containing the histone H3 variant CENP-A. The apparent epigenetic mode of centromere inheritance across mitotic and meiotic divisions has generated much interest in how CENP-A assembly occurs and how structurally divergent centromeric nucleosomes can specify the centromere complex. Although a substantial number of proteins have been implicated in centromere assembly, factors that can bind CENP-A specifically and deliver nascent protein to the centromere were, thus far, lacking. Several recent reports on experiments in fission yeast and human cells have now shown significant progress on ... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2592847 Fri, 10 Jul 2009 08:10:19 +0100 2592847 http://www.medworm.com/index.php?rid=2592848&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fnu8582q215g73681%2F In this study, we have examined the genome organization in interphase nuclei during adipogenesis, using the pig as a model organism. We hypothesized that changes in the gene expression profile and chromatin remodeling which occur during cellular differentiation would elicit repositioning of whole chromosomes, moving specific genes on them to different regions of the nucleus. We established an in vitro adipogenesis differentiation system using mesenchymal stem cells, derived from porcine bone marrow. The nuclear position of seven adipogenesis genes (PPARG, SREBF1, FABP4, CEBPA, CEBPB, CREB, and GATA2), two control genes (SOX9 and MYL1), and six chromosomes carrying these gene loci (SSC4, SSC6, SSC12, SSC13, SSC15, and SSC17) was determined. We found that during adipogenesis, using the... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2592848 Thu, 09 Jul 2009 12:11:57 +0100 2592848 http://www.medworm.com/index.php?rid=2590478&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fwp722p29m75g4x70%2F Abstract  The looping model of enhancer–promoter interactions predicts that these specific long-range interactions are supported by a certain class of proteins. In particular, the Drosophila transcription factor Zeste was hypothesized to facilitate long-distance associations between enhancers and promoters. We have re-examined the role of Zeste in supporting long-range interactions between an enhancer and a promoter using the white gene as a model system. The results show that Zeste binds to the upstream white promoter region and the enhancer that is responsible for white activation in the eyes. We have confirmed the previous finding that Zeste is not required for the activity of the eye enhancer and the promoter when they are located in close proximity to each other. Howeve... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2590478 Mon, 06 Jul 2009 20:15:11 +0100 2590478 http://www.medworm.com/index.php?rid=2579224&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fh5u725723u400167%2F Abstract  B chromosomes (Bs) are dispensable components of the genomes of numerous species. To test whether the transcriptome of a host is influenced by Bs, we looked for differences in expression in response to additional Bs. Comparative complementary DNA amplified fragment length polymorphism experiments resulted in the identification of 16 putative B-chromosome-associated transcripts. This comprises 0.7% of the total transcript number and indicates a low activity of Bs. We also provide evidence that B chromosome influences in trans the transcription of A chromosome sequences. The B-specific transcribed sequences B1334, B8149, and B2465 belong to high-copy families with similarity to mobile elements. For all analyzed B-chromosome-derived transcripts, similar A chromosome-e... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2579224 Mon, 06 Jul 2009 16:51:04 +0100 2579224 http://www.medworm.com/index.php?rid=2550004&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F65426n0472754718%2F Abstract  Synapsis of homologous chromosomes is a key meiotic event, mediated by a large proteinaceous structure termed the synaptonemal complex. Here, we describe a role in meiosis for the murine death-inducer obliterator (Dido) gene. The Dido gene codes for three proteins that recognize trimethylated histone H3 lysine 4 through their amino-terminal plant homeodomain domain. DIDO3, the largest of the three isoforms, localizes to the central region of the synaptonemal complex in germ cells. DIDO3 follows the distribution of the central region protein SYCP1 in Sycp3−/− spermatocytes, which lack the axial elements of the synaptonemal complex. This indicates that synapsis is a requirement for DIDO3 incorporation. Interestingly, DIDO3 is missing from the synaptonemal complex ... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2550004 Fri, 26 Jun 2009 07:12:48 +0100 2550004 http://www.medworm.com/index.php?rid=2500641&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fajl3208n74308833%2F Abstract  In contrast to yeast, plant interphase nuclei often display incomplete alignment (cohesion) along sister chromatid arms. Sister chromatid cohesion mediated by the multi-subunit cohesin complex is essential for correct chromosome segregation during nuclear divisions and for DNA recombination repair. The cohesin complex consists of the conserved proteins SMC1, SMC3, SCC3, and an α-kleisin subunit. Viable homozygous mutants could be selected for the Arabidopsis thaliana α-kleisins SYN1, SYN2, and SYN4, which can partially compensate each other. For the kleisin SYN3 and for the single-copy genes SMC1, SMC3, and SCC3, only heterozygous mutants were obtained that displayed between 77% and 97% of the wild-type transcript level. Compared to wild-type nuclei, sister chroma... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2500641 Wed, 17 Jun 2009 07:05:37 +0100 2500641 http://www.medworm.com/index.php?rid=2500642&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F651145wur2378246%2F Abstract  The interphase nucleus and nuclear envelope can acquire a myriad of shapes in normal or pathological cell states. There exist a wide variety of indentations and invaginations, of protrusions and evaginations. It has been difficult to classify and name all of these nuclear shapes and, consequently, a barrier to understanding the biochemical and biophysical causes. This review focuses upon one type of nuclear envelope shape change, named “nuclear envelope-limited chromatin sheets” (ELCS), which appears to involve exaggerated nuclear envelope growth, carrying with it one or more layers of ∼30 nm diameter heterochromatin. A hypothesis on the formation of ELCS is proposed, relating higher order heterochromatin structure in an interphase nucleus, nuclear enve... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2500642 Fri, 12 Jun 2009 10:43:57 +0100 2500642 http://www.medworm.com/index.php?rid=2500643&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fr072181747625001%2F Abstract  DNA methylation is a major epigenetic modification in the genomes of higher eukaryotes. In vertebrates, DNA methylation occurs predominantly on the CpG dinucleotide, and approximately 60% to 90% of these dinucleotides are modified. Distinct DNA methylation patterns, which can vary between different tissues and developmental stages, exist on specific loci. Sites of DNA methylation are occupied by various proteins, including methyl-CpG binding domain (MBD) proteins which recruit the enzymatic machinery to establish silent chromatin. Mutations in the MBD family member MeCP2 are the cause of Rett syndrome, a severe neurodevelopmental disorder, whereas other MBDs are known to bind sites of hypermethylation in human cancer cell lines. Here, we review the advances in our... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2500643 Tue, 09 Jun 2009 12:43:30 +0100 2500643 http://www.medworm.com/index.php?rid=2462381&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fy734t77024074676%2F Abstract  We have analyzed in a true bug, Graphosoma italicum (Pentatomidae, Hemiptera), the temporal and functional relationships between recombination events, synapsis progression, and SMC1α and SMC3 cohesin axis maturation throughout the male first meiotic prophase. The localization of the histone variant histone H3 trimethylated at lysine 9 at chromosome ends has allowed us to determine the association of these heterochromatic domains through prophase I stages. Results highlighted that cohesins provide to be good markers for synapsis progression since the formation, morphology, and development of the SMC1α and SMC3 cohesin axes resemble the synaptonemal complex dynamics and, also, that in this species the initiation of recombination precedes synapsis. In addition, we h... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2462381 Thu, 04 Jun 2009 10:05:40 +0100 2462381 http://www.medworm.com/index.php?rid=2445628&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F0775w54473162421%2F Content Type Journal ArticleCategory ObituaryDOI 10.1007/s00412-009-0217-5Authors Eduardo Gorab, Universidade de São Paulo Departamento de Genética e Biologia Evolutiva, Instituto de Biociências Rua do Matão 277, Cidade Universitária São Paulo São Paulo 05508-090 Brazil Journal ChromosomaOnline ISSN 1432-0886Print ISSN 0009-5915 (Source: Chromosoma) Chromosoma journals http://www.medworm.com/rss/comments.php?id=2445628 Fri, 29 May 2009 08:16:28 +0100 2445628 http://www.medworm.com/index.php?rid=2431435&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fm3h8071041h5056p%2F Abstract  The establishment of sex-specific epigenetic marks during gametogenesis is one of the key feature of genomic imprinting. By immunocytological analysis, we thoroughly characterized the chromatin remodeling events that take place during gametogenesis in the mealybug Planococcus citri, in which an entire haploid set of (imprinted) chromosomes undergoes facultative heterochromatinization in male embryos. Building on our previous work, we have investigated the interplay of several epigenetic marks in the regulation of this genome-wide phenomenon. We characterized the germline patterns of histone modifications, Me(3)K9H3, Me(2)K9H3, and Me(3)K20H4, and of heterochromatic proteins, PCHET2 (HP1-like) and HP2-like during male and female gametogenesis. We found that at all s... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2431435 Thu, 21 May 2009 06:15:54 +0100 2431435 http://www.medworm.com/index.php?rid=2426456&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fv8803jx203r24577%2F Abstract  The zebra finch (Taeniopygia guttata) germline-restricted chromosome (GRC) is the largest chromosome and has a unique system of transmission in germ cells. In the male, the GRC exists as a single heterochromatic chromosome in the germline and is eliminated from nuclei in late spermatogenesis. In the female, the GRC is bivalent and euchromatic and experiences recombination. These characteristics suggest a female-specific or female-beneficial function of the GRC. To shed light on the function of GRC, we cloned a portion of the GRC using random amplified polymorphic DNA–polymerase chain reaction and analyzed it using molecular genetic and cytogenetic methods. The GRC clone hybridized strongly to testis but not blood DNA in genomic Southern blots. In fluorescent in s... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2426456 Tue, 19 May 2009 05:54:48 +0100 2426456 http://www.medworm.com/index.php?rid=2395713&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fk33512w631767766%2F Abstract  The organization of chromosomes into euchromatin and heterochromatin is amongst the most important and enigmatic aspects of genome evolution. Constitutive heterochromatin is a basic yet still poorly understood component of eukaryotic chromosomes, and its molecular characterization by means of standard genomic approaches is intrinsically difficult. Although recent evidence indicates that the presence of transcribed genes in constitutive heterochromatin is a conserved trait that accompanies the evolution of eukaryotic genomes, the term heterochromatin is still considered by many as synonymous of gene silencing. In this paper, we comprehensively review data that provide a clearer picture of transcribed sequences within constitutive heterochromatin, with a special emp... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2395713 Sat, 02 May 2009 06:24:59 +0100 2395713 http://www.medworm.com/index.php?rid=2395712&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fu357057481167476%2F Abstract  Puffs in the polytene chromosome of Drosophila melanogaster are characteristic of sites of high-level active transcription which can be observed directly under the microscope. We studied the dependence of puff formation on chromatin modifications at a site where a GAL4-inducible transgene is located in the 61C7 cytological region. Immunostaining of salivary gland polytene chromosomes indicated no increase of either dSAGA-specific histone H3 lysine 14, or ATAC-specific histone H4 lysine 5 and 12 acetylation in the puffed region. Nor did we observe increased levels of H4K8ac, H3K18ac, or H4K16ac in the puff. In accordance with the above, puff formation as well as localization of Pol II and GAL4 was detectable at the 61C region in dAda2b and dAda2a null homozygotes, w... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2395712 Sat, 02 May 2009 06:24:59 +0100 2395712 http://www.medworm.com/index.php?rid=2385775&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fn57667t10476x2m2%2F Abstract  In 1906, the Spanish neurobiologist Santiago Ramón y Cajal was awarded the Nobel Prize in Physiology or Medicine in recognition of his work on the structure of neurons and their connections. Cajal is commonly regarded as the father of modern neuroscience. What is less well known is that Cajal also had a great interest in intracellular neuronal structures and developed the reduced silver nitrate method for the study of neurofibrils (neurofilaments) and nuclear subcompartments. It was in 1903 that Cajal discovered the “accessory body” (“Cajal body”) and seven years later, published an article on the organization of the cell nucleus in mammalian neurons that represents a masterpiece of nuclear structure at the light microscopy level. In addition to the acces... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2385775 Thu, 30 Apr 2009 06:03:18 +0100 2385775 http://www.medworm.com/index.php?rid=2373486&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Ff18054278l575477%2F Abstract  Histones of trypanosomes are quite divergent when compared to histones of most eukaryotes. Nevertheless, the histone H4 of Trypanosoma cruzi, the protozoan that causes Chagas’ disease, is acetylated in the N terminus at lysines 4, 10, and 14. Here, we investigated the cellular distribution of histone H4 containing each one of these posttranslational modifications by using specific antibodies. Histone H4 acetylated at lysine 4 (H4-K4ac) is found in the entire nuclear space preferentially at dense chromatin regions, excluding the nucleolus of replicating epimastigote forms of the parasite. In contrast, histone H4 acetylated either at K10 or K14 is found at dispersed foci all over the nuclei and at the interface between dense and nondense chromatin areas as observed... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2373486 Sat, 25 Apr 2009 07:28:07 +0100 2373486 http://www.medworm.com/index.php?rid=2373487&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F710230t10314r625%2F Abstract  The Mre11-Rad50-Nbs1 (MRN) complex is required for numerous cellular processes that involve interactions with DNA double-strand breaks. For the majority of these processes, the MRN complex is thought to act as a unit, with each protein aiding the activity of the others. We have examined the relationship between Mre11 and Rad50 during meiosis in the basidiomycete Coprinus cinereus (Coprinopsis cinerea), investigating to what extent activities of Mre11 and Rad50 are interdependent. We showed that mre11-1 is epistatic to rad50-1 with respect to the time of meiotic arrest, indicating that Mre11 activity facilitates the diffuse diplotene arrest of rad50 mutants. Anti-Mre11 and anti-Rad50 antibodies were used to examine MRN complex localization in a wild-type strain and in ... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2373487 Sat, 25 Apr 2009 07:28:06 +0100 2373487 http://www.medworm.com/index.php?rid=2321229&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fy38376216137p471%2F Abstract  MicroRNAs (miRNAs) were first discovered in genetic screens for regulators of developmental timing in the stem-cell-like seam cell lineage in Caenorhabditis elegans. As members of the heterochronic pathway, the lin-4 and let-7 miRNAs are required in the seam cells for the correct progression of stage-specific events and to ensure that cell cycle exit and terminal differentiation occur at the correct time. Other heterochronic genes such as lin-28 and lin-41 are direct targets of the lin-4 and let-7 miRNAs. Recent findings on the functions of the let-7 and lin-4/mir-125 miRNA families and lin-28 and lin-41 orthologs from a variety of organisms suggest that core elements of the heterochronic pathway are retained in mammalian stem cells and development. In particular, th... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2321229 Thu, 02 Apr 2009 05:51:20 +0100 2321229 http://www.medworm.com/index.php?rid=2281686&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fw4278w42m1862u22%2F Abstract  Chromosomal replication results in the duplication not only of DNA sequence but also of the patterns of histone modification, DNA methylation, and nucleoprotein structure that constitute epigenetic information. Pericentromeric heterochromatin in human cells is characterized by unique patterns of histone and DNA modification. Here, we describe association of the Mi-2/NuRD complex with specific segments of pericentromeric heterochromatin consisting of Satellite II/III DNA located on human chromosomes 1, 9, and 16 in some but not all cell types. This association is linked in part to DNA replication and chromatin assembly and may suggest a role in these processes. Mi-2/NuRD accumulation is independent of Polycomb association and is characterized by a unique pattern of... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2281686 Fri, 20 Mar 2009 09:53:08 +0100 2281686 http://www.medworm.com/index.php?rid=2281687&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fvtp38770814q5153%2F In this study, a bio-computational approach is employed to simultaneously measure the translational motion of large populations of ChrD in the cell nucleus of living cells. Both movement and configurational changes are strikingly higher in early S-phase replicating ChrD compared to those that replicate in mid and late S-phase. The chromatin dynamics was not sensitive to transcription inhibition by α-amanitin but was significantly reduced by actinomycin D treatment. Since a majority of active genes replicate in early S-phase, our results suggest a correlation between levels of chromatin dynamics and chromatin poised for active transcription. Analysis of ChrD colocalization with transcription sites and cDNA with ChrD and transcription sites further supports this proposal. Content T... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2281687 Fri, 20 Mar 2009 09:53:06 +0100 2281687 http://www.medworm.com/index.php?rid=2221391&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fl165660728242321%2F Abstract  The life cycle of animals and plants involves changes in chromosome number (nuclear phase) and sometimes even the karyotype, and consequently the DNA content of a nuclear genome is not static in time. Thus, in order to interpret DNA content data, it is important that the status of the materials from which DNA content is estimated be precisely defined. The previously proposed distinction between “holoploid” (C) and “monoploid” (Cx) genome size covers the most frequent states of plant and animal nuclear genomes. However, restricting nomenclature to just C and Cx still leaves a number of unresolved problems. Here, we propose an extension of the C-value terminology to handle a range of cytogenetic conditions, life cycle segments, and nuclear phases. A set of s... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2221391 Thu, 26 Feb 2009 10:34:22 +0100 2221391 http://www.medworm.com/index.php?rid=2221392&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fc26u20u01l6v734q%2F Abstract  Three systems of monoallelic gene expression in mammals are known, namely, X-chromosome inactivation, imprinting, and allelic exclusion. In all three systems, monoallelic expression is regulated epigenetically and is frequently directed by long non-coding RNAs (ncRNAs). This review briefs all three systems of monoallelic gene expression in mammals focusing on chromatin modifications, spatial chromosome organization in the nucleus, and the functioning of ncRNAs. Content Type Journal ArticleCategory ReviewDOI 10.1007/s00412-009-0206-8Authors Irina S. Zakharova, Russian Academy of Sciences Siberian Department, Institute of Cytology and Genetics Novosibirsk RussiaAlexander I. Shevchenko, Russian Academy of Sciences Siberian Department, Institute of Cytology and Gene... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2221392 Thu, 26 Feb 2009 10:34:21 +0100 2221392 http://www.medworm.com/index.php?rid=2215556&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fju7685636l291331%2F Abstract  One of the subjects within the meiotic field that has been actively investigated in the recent years is the temporal and functional relationships between meiotic recombination, cohesin loading and synaptonemal complex (SC) assembly. Although the study of meiotic mutants has shed some light, many questions remain to be answered. Here, we have studied this topic in the orthopteran Paratettix meridionalis, a species with telocentric chromosomes, which shows two unusual cytological features: pairing and synapsis of homologues during prophase I are restricted to the non-centromeric distal regions and extremely distal chiasma localization in metaphase I bivalents. In order to determine whether there is a relationship between both phenomena, we have used: (1) a spreading ... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2215556 Tue, 24 Feb 2009 09:44:38 +0100 2215556 http://www.medworm.com/index.php?rid=2500644&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fu3t05w41j67w2831%2F We report here the molecular and cytological characterization of two proteins, ScoHET1 and ScoHET2 (for Sciara coprophila heterochromatin), which associate to constitutive heterochromatin in the dipteran S. coprophila. Both proteins, ScoHET1 of 37 kDa and ScoHET2 of 44 kDa, display two chromodomain motifs that contain the conserved residues essential for the recognition of methylated histone H3 at lysine 9. We raised antibodies to analyze the chromosomal location of ScoHET1 and ScoHET2 in somatic and germline cells. In S. coprophila polytene chromosomes, both proteins associate to the pericentromeric regions and to the heterochromatic subterminal bands of the chromosomes. In germinal nuclei, ScoHET1 and ScoHET2 proteins distribute to the heterochromatic regions of the regular ... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2500644 Wed, 11 Feb 2009 06:57:02 +0100 2500644 http://www.medworm.com/index.php?rid=2181533&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fu3t05w41j67w2831%2F We report here the molecular and cytological characterization of two proteins, ScoHET1 and ScoHET2 (for Sciara coprophila heterochromatin), which associate to constitutive heterochromatin in the dipteran S. coprophila. Both proteins, ScoHET1 of 37 kDa and ScoHET2 of 44 kDa, display two chromodomain motifs that contain the conserved residues essential for the recognition of methylated histone H3 at lysine 9. We raised antibodies to analyze the chromosomal location of ScoHET1 and ScoHET2 in somatic and germline cells. In S. coprophila polytene chromosomes, both proteins associate to the pericentromeric regions and to the heterochromatic subterminal bands of the chromosomes. In germinal nuclei, ScoHET1 and ScoHET2 proteins distribute to the heterochromatic regions of the regular ... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2181533 Wed, 11 Feb 2009 06:57:02 +0100 2181533 http://www.medworm.com/index.php?rid=2171999&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F1342m1n1n4358g85%2F Abstract  Whether chromosome sets inherited from father and mother occupy separate spaces in the cell nucleus is a question first asked over 110 years ago. Recently, the nuclear organization of the genome has come increasingly into focus as an important level of epigenetic regulation. In this context, it is indispensable to know whether or not parental genomes are spatially separated. Genome separation had been demonstrated for plant hybrids and for the early mammalian embryo. Conclusive studies for somatic mammalian cell nuclei are lacking because homologous chromosomes from the two parents cannot be distinguished within a species. We circumvented this problem by investigating the three-dimensional distribution of chromosomes in mule lymphocytes and fibroblasts. Genom... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2171999 Sat, 07 Feb 2009 10:09:46 +0100 2171999 http://www.medworm.com/index.php?rid=3095607&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F8627n084hh3564q0%2F In this study, we have characterized the breakpoint regions of inversion 5g, fixed in D. buzzatii and absent in Drosophila koepferae and other closely related species. A novel approach comprising four experimental steps was used. First, D. buzzatii BAC clones encompassing the breakpoints were identified and their ends sequenced. Then, breakpoint regions were mapped at high resolution in the Drosophila mojavensis genome sequence. Finally, breakpoint regions were isolated by polymerase chain reaction in D. buzzatii and D. koepferae and sequenced. Our aim was to shed light on the mechanism that generated inversion 5g and specifically to test for an implication of the transposon Galileo. No evidence implicates Galileo or other transposable elements in the origin of inversion 5g that was gener... Chromosoma journals http://www.medworm.com/rss/comments.php?id=3095607 Sat, 07 Feb 2009 10:09:44 +0100 3095607 http://www.medworm.com/index.php?rid=2172000&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F8627n084hh3564q0%2F In this study, we have characterized the breakpoint regions of inversion 5g, fixed in D. buzzatii and absent in Drosophila koepferae and other closely related species. A novel approach comprising four experimental steps was used. First, D. buzzatii BAC clones encompassing the breakpoints were identified and their ends sequenced. Then, breakpoint regions were mapped at high resolution in the Drosophila mojavensis genome sequence. Finally, breakpoint regions were isolated by polymerase chain reaction in D. buzzatii and D. koepferae and sequenced. Our aim was to shed light on the mechanism that generated inversion 5g and specifically to test for an implication of the transposon Galileo. No evidence implicates Galileo or other transposable elements in the origin of inversion 5g that was gener... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2172000 Sat, 07 Feb 2009 10:09:44 +0100 2172000 http://www.medworm.com/index.php?rid=2159849&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fa3601p8107633758%2F Content Type Journal ArticleCategory ObituaryDOI 10.1007/s00412-009-0202-zAuthors Antoni Rafalski, DuPont Co./Pioneer Hi-Bred Wilmington DE 19807 USA Journal ChromosomaOnline ISSN 1432-0886Print ISSN 0009-5915 (Source: Chromosoma) Chromosoma journals http://www.medworm.com/rss/comments.php?id=2159849 Tue, 03 Feb 2009 07:15:14 +0100 2159849 http://www.medworm.com/index.php?rid=2103961&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fm64v74305252v227%2F In this study, we analyzed the gene FEM1C which is highly conserved from Caenorhabditis elegans to higher vertebrates and interacts with the sex determining pathway in C. elegans. We found that FEM1C is located on the Z and W chromosome of zebra finches and probably other Passerine birds, but shows only Z linkage in other avian orders. In the zebra finch, FEM1C-W is degraded because of a point mutation and possibly because of loss of the first exon containing the start methionine. Thus, FEM1C-W appears to have degenerated or been lost from most bird species. FEM1C-Z is expressed in a cytoplasmic location in zebra finch fibroblast cells, as in C. elegans. FEM1C represents an interesting example of evolutionary degradation of a W chromosome gene. Content Type Journal ArticleCategory Res... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2103961 Tue, 13 Jan 2009 08:23:56 +0100 2103961 http://www.medworm.com/index.php?rid=2032331&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Ft284u8t1441u0112%2F Abstract  Ribosomal DNA genes (rDNA) are found in tandem arrays of hundreds of repeated genes, but only a fraction of these genes are actively transcribed. The regulatory mechanism controlling the transition between active and inactive rDNA in higher eukaryotes is vital for cell survival. Here, we show that the nucleolus from Drosophila salivary gland cells contains two levels of chromatin organization reflecting differences in transcriptional activity: Decondensed chromatin is highly occupied with TATA-box-binding protein (TBP), phosphorylated H3S10, and acetylated H3K14, suggesting that rDNA in decondensed nucleolar areas is actively transcribed. Condensed chromatin lacks TBP, phosphorylated H3S10, or acetylated H3K14 and is enriched in the rDNA retrotransposons R1 and R2.... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2032331 Wed, 10 Dec 2008 07:55:11 +0100 2032331 http://www.medworm.com/index.php?rid=2032330&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fb417642hl4631408%2F Abstract  The endocycle constitutes an effective strategy for cell growth during development. In contrast to the mitotic cycle, it consists of multiple S-phases with no intervening mitosis and lacks a checkpoint ensuring the replication of the entire genome. Here, we report an essential requirement of chromatin assembly factor-1 (CAF-1) for Drosophila larval endocycles. This complex promotes histone H3–H4 deposition onto newly synthesised DNA in vitro. In metazoans, the depletion of its large subunit leads to the rapid accumulation of cells in S-phase. However, whether this slower S-phase progression results from the activation of cell cycle checkpoints or whether it reflects a more direct requirement of CAF-1 for efficient replication in vivo is still debated. Here, we sh... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2032330 Wed, 10 Dec 2008 07:55:11 +0100 2032330 http://www.medworm.com/index.php?rid=2010538&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fn1w3502074818233%2F Abstract  Although the human genome sequence is generally considered “finished”, the latest assembly (NCBI Build 36.1) still presents a number of gaps. Some of them are defined as “clone gaps” because they separate neighboring contigs. Evolutionary new centromeres are centromeres that repositioned along the chromosome, without marker order variation, during evolution. We have found that one human “clone gap” at 18q21.2 corresponds to an evolutionary new centromere in Old World Monkeys (OWM). The partially sequenced gap revealed a satellite-like structure. DNA stretches of the same satellite were found in the macaque (flanking the chromosome 18 centromere) and in the marmoset (New World Monkey), which was used as an outgroup. These findings strongly suggested that... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2010538 Tue, 02 Dec 2008 07:32:12 +0100 2010538 http://www.medworm.com/index.php?rid=2010537&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F764434l562416660%2F Abstract  Centromeres play an important role in segregating chromosomes into daughter cells, and centromeric DNA assembles specific proteins to form a complex referred to as the kinetochore. Among these proteins, centromere-specific histone H3 (CENH3) is one of the most characterized and found to be located only on active centromeres. We isolated four different CENH3-coding complementary DNAs (cDNAs), two from Nicotiana tabaccum and one each from the ancestral diploid species, Nicotiana sylvestris and Nicotiana tomentosiformis and raised an antibody against N-terminal amino acid sequences deduced from the cDNAs. Immunostaining with the antibody revealed the preferential centromere localization, indicating that the cDNAs cloned in this study encode authentic tobacco CENH3. A ... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2010537 Tue, 02 Dec 2008 07:32:12 +0100 2010537 http://www.medworm.com/index.php?rid=2010539&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fe8143006l5123734%2F Abstract  The B24 chromosome in the Torrox population of the grasshopper Eyprepocnemis plorans is recurrently attached to a nucleolus in diplotene cells, indicating the activity of its distally located ribosomal DNA (rDNA). The frequency of males expressing the B chromosome nucleolus organizer region (B-NOR) almost doubled in 4 years. The likelihood of expressing the B-NOR increased with the B number and, in males expressing it, about 20% of their cells showed a nucleolus attached to the B. When active, the B-NOR contributed more than 25% of total cell nucleolar area (NA). Within males expressing the B-NOR, total cell NA did not differ between cells showing the active or inactive B-NOR, suggesting that total cell NA is tightly regulated in this species. However, this pa... Chromosoma journals http://www.medworm.com/rss/comments.php?id=2010539 Tue, 02 Dec 2008 07:32:11 +0100 2010539 http://www.medworm.com/index.php?rid=1995570&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fr3j2011210736n14%2F Abstract  Synaptonemal complexes (SCs) are evolutionarily conserved meiosis-specific nuclear structures critically involved in synapsis, recombination, and segregation of homologous chromosomes. SCs are proteinaceous structures composed of (a) two lateral elements (LEs), to which the chromatin of the homologs is attached, (b) numerous transverse filaments (TFs) that link the LEs, and (c) a central element (CE). Major protein components of mammalian SCs are the TF protein SYCP1 and the LE proteins SYCP2 and SCYP3. How SCs become assembled is presently poorly understood, in particular, it is not known how TFs assemble at the plane of LEs to interconnect the homologous chromosomes. Therefore, we have investigated possible interactions between SYCP1 and other SC proteins. In im... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1995570 Wed, 26 Nov 2008 19:58:43 +0100 1995570 http://www.medworm.com/index.php?rid=1984266&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fp5714853q50t84mm%2F Abstract  Over the last few years, there has been a convergence of two seemingly disparate fields of study: chromatin-dependent gene silencing and RNA turnover. In contrast to RNA turnover mechanisms that operate on a truly posttranscriptional level, we are at the beginning of studies leading the way toward a model in which RNA turnover mechanisms are also involved in chromatin-dependent gene regulation. In particular, data from a variety of organisms have shown that the assembly of silent chromatin coincides with the presence or absence of non-protein-coding RNAs (ncRNAs). These range from long ncRNAs that have been classically implicated in the regulation of dosage compensation and genomic imprinting to small ncRNAs which are involved in heterochromatin assembly via the R... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1984266 Fri, 21 Nov 2008 06:55:42 +0100 1984266 http://www.medworm.com/index.php?rid=1974198&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fx878n064082r4436%2F We report on the construction of maize minichromosomes using shuttle vectors harboring native centromeric segments, origins of replication, selectable marker genes, and telomeric repeats. These vectors were introduced into scutellar cells of maize immature embryos by microprojectile bombardment. Several independent transformation events were identified containing minichromosomes in addition to the normal diploid complement of 20 maize chromosomes. Immunostaining indicated that the minichromosomes recruited centromeric protein C, which is a specific component of the centromere/kinetochore complex. Minichromosomes were estimated to be 15–30 Mb in size based on cytological measurements. Fluorescent in situ hybridization (FISH) showed that minichromosomes contain the centromeric, ... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1974198 Tue, 18 Nov 2008 08:00:37 +0100 1974198 http://www.medworm.com/index.php?rid=1974197&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F7476457th18w2182%2F Abstract  Loss of heterozygosity (LOH) of tumor suppressor genes in somatic cells is a major process leading to several types of cancer; however, its underlying molecular mechanism is still poorly understood. In the present work, we demonstrate that a linear DNA molecule bridging two homologous chromosomes in diploid yeast cells via homologous recombination produce LOH-generating regions of hemizygosity by deletion. The result is a near-reciprocal translocation mutant that is characterized by slight cell cycle defects and increased expression of the multidrug-resistant gene VMR1. When the distance between target regions is approximately 40 kb, the specificity of gene targeting becomes less stringent and an ensemble of gross chromosomal rearrangements arises. These heter... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1974197 Tue, 18 Nov 2008 08:00:37 +0100 1974197 http://www.medworm.com/index.php?rid=1959331&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fk00121284k035685%2F Abstract  Mammalian X chromosome inactivation (XCI) is an essential mechanism to compensate for dosage imbalances between male and female embryos. Although the molecular pathways are not fully understood, heterochromatinization of the Xi requires the coordinate recruitment of multiple epigenetic marks. Using fluorescence in situ hybridization analysis combined with immunocytochemistry, we demonstrate that the chromatin remodeling protein ATRX decorates the chromatids of a single, late replicating X chromosome in female somatic cells and co-localizes with the bona fide marker of the Xi, macroH2A1.2. Chromatin immunoprecipitation using somatic, embryonic stem (ES) cells and trophoblast stem (TS) cells as model for random and imprinted XCI, respectively, revealed that, in soma... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1959331 Thu, 13 Nov 2008 15:45:16 +0100 1959331 http://www.medworm.com/index.php?rid=1944695&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fj96g35t6128nv283%2F Abstract  Sister chromatid cohesion is mediated by cohesin. At the onset of mitosis, most cohesin dissociates from chromatin with the exception of a small population, present along chromosome arms and enriched at centromeres. A protein known as shugoshin (Sgo) is essential to maintain arm and centromeric cohesion until the onset of anaphase in transformed human cells, but not in other organisms like Drosophila or mouse. We have used Xenopus egg extracts to further explore this issue. Chromosomes assembled in extracts depleted of Sgo have little or no cohesin at centromeres and display centromeric cohesion defects. Unlike transformed human cells, however, arm cohesion is maintained in the absence of Sgo. Furthermore, Sgo depletion impairs the prophase dissociation of cohesin... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1944695 Thu, 06 Nov 2008 07:04:43 +0100 1944695 http://www.medworm.com/index.php?rid=1938031&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fnl4478uu518823q7%2F Abstract  Actins are highly conserved proteins that serve as the basic building blocks of cytoskeletal microfilaments. In animal cells, specific nuclear actin adopts unconventional conformations that are involved in multiple nuclear functions and that associate with nuclear actin binding proteins. However, there is practically no information available about nuclear actin in plants. Indeed, actin has not been detected in the nuclear proteomes of many plants, and orthologs of the main structural nuclear actin-binding proteins have yet to be identified. Here, we have investigated the characteristics, intranuclear compartmentalization, and function of actin in isolated Allium cepa nuclei as well as that of its motor protein nuclear myosin I (NMI). Using conformation-specific ant... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1938031 Tue, 04 Nov 2008 07:10:10 +0100 1938031 http://www.medworm.com/index.php?rid=1900331&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F45852557852220t1%2F In this study, the subnuclear localization of two gene clusters repressed by nitrogen was investigated. During normal growth conditions, the gene clusters localized to the nuclear periphery at the opposite side of the nucleus as compared to the spindle pole body. This constrained localization was dependent on the histone deacetylase Clr3, known to transcriptionally repress genes in these clusters. Already 20 min after nitrogen depletion, drastic changes in subnuclear localization of the two loci were observed, away from the NM toward the nuclear interior. At least for one of the clusters, the movement was clearly transcription dependent. Data presented in this paper illustrates how interconnected events of gene activation and nuclear reorganization are as well as provides a sugg... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1900331 Tue, 21 Oct 2008 06:12:16 +0100 1900331 http://www.medworm.com/index.php?rid=1887851&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F96r228660223p848%2F Abstract  The nucleolus is an informative model structure for studying how chromatin-regulated transcription relates to nuclear organisation. In this review, we describe how chromatin controls nucleolar structure through both the modulation of rDNA activity by convergently-evolved remodelling complexes and by direct effects upon rDNA packaging. This packaging not only regulates transcription but may also be important for suppressing internal recombination between tandem rDNA repeats. The identification of nucleolar histone chaperones and novel chromatin proteins by mass spectrometry suggests that structure-specific chromatin components remain to be characterised and may regulate the nucleolus in novel ways. However, it also suggests that there is considerable overlap between... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1887851 Fri, 17 Oct 2008 08:51:49 +0100 1887851 http://www.medworm.com/index.php?rid=1879279&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fw5qg7n861748j536%2F Abstract  In genomes of higher eukaryotes, adjacent genes often show coordinated regulation of their expression. Compartmentalization of multiple neighboring genes into a shared chromatin environment can facilitate this coordinated expression. New mapping techniques have begun to reveal that such multigene chromatin domains are a common feature of fly and mammalian genomes. Many different types of chromatin domains have been identified based on the genomic binding patterns of various proteins and histone modifications. In addition, maps of genome–nuclear lamina associations and of looping interactions between loci provide the first systematic views of the three-dimensional folding of interphase chromosomes. These genome-wide datasets uncover new architectural principles o... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1879279 Tue, 14 Oct 2008 11:24:26 +0100 1879279 http://www.medworm.com/index.php?rid=1865063&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fk87241r366g6050k%2F Abstract  Mer3 is an evolutionarily conserved DNA helicase that has crucial roles in meiotic recombination and crossover formation. We have identified the MER3 homolog in Coprinus cinereus (Ccmer3) and show that it is expressed in zygotene and pachytene meiocytes. Immunostaining analysis indicated that CcMer3 was localized on chromosomes at zygotene and pachytene and CcMer3 foci were more frequent on paired than unpaired chromosomes. We generated a C. cinereus mer3 mutant (#1) and found that it showed abnormal meiosis progression and underwent apoptosis after prophase I. Basidiospore production in #1 was reduced to 0.8% of the wild-type level; the spores showed slower germination at 25°C but were similar to the wild type at 37°C. Electron microscopic analysis of chromosome... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1865063 Wed, 08 Oct 2008 12:14:03 +0100 1865063 http://www.medworm.com/index.php?rid=1865065&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fr662713351177513%2F Abstract  The transcriptional framework of the eukaryotic centromere core has been described in budding yeast and rice, but for most eukaryotes and all vertebrates it remains largely unknown. The lack of large pericentric repeats in the tammar wallaby has made it possible to map and identify the transcriptional units at the centromere in a mammalian species for the first time. We show that these transcriptional units, comprised of satellites and a retrovirus, are bound by centromere proteins and that they are the source of a novel class of small RNA. The endogenous retrovirus from which these small RNAs are derived is now known to be in the centromere domain of several vertebrate classes. The discovery of this new RNA form brings together several independent lines of eviden... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1865065 Wed, 08 Oct 2008 09:50:20 +0100 1865065 http://www.medworm.com/index.php?rid=1865064&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F28688637346r3586%2F Abstract  Gene silencing by DNA methylation is well documented and known to be essential for various biological phenomena in many organisms. In contrast, the processes that convert the silent state of a gene whose DNA is methylated and predicted to form facultative heterochromatin to the actively transcribed state remain elusive. In Arabidopsis, recent studies have shown that the DNA glycosylases DEMETER (DME) and REPRESSOR OF SILENCING1 (ROS1) participate in DNA demethylation. DME is necessary for genomic imprinting in the endosperm, while ROS1 is involved in pruning DNA methylation patterns in transposons and genic regions of vegetative tissues. These findings provide us with molecular clues for understanding the underlying mechanisms of DNA demethylation and gene activati... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1865064 Wed, 08 Oct 2008 09:50:20 +0100 1865064 http://www.medworm.com/index.php?rid=1850358&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fwl13806508805wm2%2F Abstract  The past two decades of research into transcriptional control of protein-encoding genes in eukaryotes have focused on regulatory mechanisms that act by controlling the recruitment of Pol II to a gene’s promoter. Recent genome-wide analyses of the distribution of Pol II indicates that Pol II is concentrated in the promoter regions of thousands of genes in human and Drosophila cells. In many cases, Pol II may have initiated transcription but paused in the promoter proximal region. Hence, release of Pol II from the promoter region into the body of a gene is now recognized as a common rate-limiting step in the control of gene expression. Notably, most genes with paused Pol II are expressed indicating that the pause can be transient. What causes Pol II to concentrate ... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1850358 Thu, 02 Oct 2008 09:27:23 +0100 1850358 http://www.medworm.com/index.php?rid=1789870&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fg772333619203g38%2F Abstract  Incenp is an essential mitotic protein that, together with Aurora B, Survivin, and Borealin, forms the core of the chromosomal passenger protein complex (CPC). The CPC regulates various mitotic processes and functions to maintain genomic stability. The proper subcellular localization of the CPC and its full catalytic activity require the presence of each core subunit in the complex. We have investigated the mitotic tasks of the CPC using a function blocking antibody against Incenp microinjected into cells at different mitotic phases. This method allowed temporal analysis of CPC functions without perturbation of complex assembly or activity prior to injection. We have also studied the dynamic properties of Incenp and Aurora B using fusion protein photobleaching. We... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1789870 Thu, 11 Sep 2008 08:50:41 +0100 1789870 http://www.medworm.com/index.php?rid=1782003&cid=s_33449_50_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fu517x77571tm0l22%2F Abstract  Typically in plants, the 5S and 35S ribosomal DNA (rDNA) encoding two major ribosomal RNA species occur at separate loci. However, in some algae, bryophytes and ferns, they are at the same locus (linked arranged). Southern blot hybridisation, polymerase chain reactions (PCR), fluorescent in situ hybridisation, cloning and sequencing were used to reveal 5S and 35S rDNA genomic organisation in Artemisia. We observed thousands of rDNA units at two–three loci containing 5S rDNA in an inverted orientation within the inter-genic spacer (IGS) of 35S rDNA. The sequenced clones of 26–18S IGS from Artemisia absinthium appeared to contain a conserved 5S gene insertion proximal to the 26S gene terminus (5S rDNA-1) and a second less conserved 5S insertion (5S rDNA-2) furthe... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1782003 Tue, 09 Sep 2008 09:05:52 +0100 1782003 http://www.medworm.com/index.php?rid=1741876&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fk6971j536h7x7777%2F Abstract  In mammals, chromosomes occupy defined positions in sperm, whereas previous work in chicken showed random chromosome distribution. Monotremes (platypus and echidnas) are the most basal group of living mammals. They have elongated sperm like chicken and a complex sex chromosome system with homology to chicken sex chromosomes. We used platypus and chicken genomic clones to investigate genome organization in sperm. In chicken sperm, about half of the chromosomes investigated are organized non-randomly, whereas in platypus chromosome organization in sperm is almost entirely non-random. The use of genomic clones allowed us to determine chromosome orientation and chromatin compaction in sperm. We found that in both species chromosomes maintain orientation of chromosomes... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1741876 Tue, 26 Aug 2008 08:16:27 +0100 1741876 http://www.medworm.com/index.php?rid=1691412&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fhp77252g0v136u20%2F Abstract  Populations of the gecko lizard Gekko hokouensis (Gekkonidae, Squamata) on Okinawajima Island and a few other islands of the Ryukyu Archipelago, Japan, have the morphologically differentiated sex chromosomes, the acrocentric Z chromosome and the subtelocentric W chromosome, although the continental representative of this species reportedly shows no sex chromosome heteromorphism. To investigate the origin of sex chromosomes and the process of sex chromosomal differentiation in this species, we molecularly cloned the homologues of six chicken Z-linked genes and mapped them to the metaphase chromosomes of the Okinawajima sample. They were all localized to the Z and W chromosomes in the order ACO1/IREBP–RPS6–DMRT1–CHD1–GHR–ATP5A1, indicating that the origin o... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1691412 Thu, 07 Aug 2008 09:59:44 +0100 1691412 http://www.medworm.com/index.php?rid=1685692&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fe26x31u011002756%2F Abstract  Distal location of chiasmata in chromosome arms is thought to be a consequence of the distal initiation of synapsis. Observations of meiotic behavior of a rye chromosome with an inverted arm show that patterns of chiasma distribution and frequency are also inverted; therefore, the patterns of synapsis and chiasma distribution are independent, and recombination frequency along a chromosome is position-independent and segment-specific. Since cases of random distribution of chiasmata and recombination are known in rye, a genetic mechanism must be present that licenses specific chromosome regions for recombination. Large differences in the metaphase I pairing of the inversion in various combinations of two armed and telocentric chromosomes confirm the major role of th... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1685692 Tue, 05 Aug 2008 07:11:07 +0100 1685692 http://www.medworm.com/index.php?rid=1678887&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fn448425051472407%2F Abstract  To maintain their genetic integrity, eukaryotic cells must segregate their chromosomes properly to opposite poles during mitosis. This process mainly depends on the forces generated by microtubules that attach to kinetochores. During prometaphase, kinetochores initially interact with a single microtubule that extends from a spindle pole and then move towards a spindle pole. Subsequently, microtubules that extend from the other spindle pole also interact with kinetochores and, eventually, each sister kinetochore attaches to microtubules that extend from opposite poles (sister kinetochore bi-orientation). If sister kinetochores interact with microtubules in wrong orientation, this must be corrected before the onset of anaphase. Here, I discuss the processes leading ... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1678887 Sat, 02 Aug 2008 06:54:39 +0100 1678887 http://www.medworm.com/index.php?rid=1654912&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fgx8662622140j485%2F Abstract  Chromosomes occupy non-random spatial positions in interphase nuclei. It remains unclear what orchestrates this high level of organisation. To determine how the nuclear environment influences the spatial positioning of chromosomes, we utilised a panel of stable mouse hybrid cell lines carrying a single, intact human chromosome. Eleven of 22 human chromosomes revealed an alternative location in hybrid nuclei compared to that of human fibroblasts, with the majority becoming more internally localised. Human chromosomes in mouse nuclei position according to neither their gene density nor size, but rather the position of human chromosomes in hybrid nuclei appears to mimic that of syntenic mouse chromosomes. These results suggest that chromosomes adopt the behaviour of ... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1654912 Thu, 24 Jul 2008 08:57:29 +0100 1654912 http://www.medworm.com/index.php?rid=1581619&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F9732p457640873nj%2F Abstract  To study when and where active genes replicated in early S phase are transcribed, a series of pulse-chase experiments are performed to label replicating chromatin domains (RS) in early S phase and subsequently transcription sites (TS) after chase periods of 0 to 24 h. Surprisingly, transcription activity throughout these chase periods did not show significant colocalization with early RS chromatin domains. Application of novel image segmentation and proximity algorithms, however, revealed close proximity of TS with the labeled chromatin domains independent of chase time. In addition, RNA polymerase II was highly proximal and showed significant colocalization with both TS and the chromatin domains. Based on these findings, we propose that chromatin activated f... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1581619 Fri, 04 Jul 2008 05:56:03 +0100 1581619 http://www.medworm.com/index.php?rid=1576946&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fu13563633101521w%2F Abstract  To understand the regulation of the genome, it is necessary to understand its three-dimensional organization in the nucleus. We investigated the positioning of eight gene loci on four different chromosomes, including the β-globin gene, in mouse embryonic stem cells and in in vitro differentiated macrophages by fluorescence in situ hybridization on structurally preserved nuclei, confocal microscopy, and 3D quantitative image analysis. We found that gene loci on the same chromosome can significantly differ from each other and from their chromosome territory in their average radial nuclear position. Radial distribution of a given gene locus can change significantly between cell types, excluding the possibility that positioning is determined solely by the DNA sequenc... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1576946 Thu, 03 Jul 2008 08:17:12 +0100 1576946 http://www.medworm.com/index.php?rid=1534849&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Ft8365428702600k6%2F Abstract  Formation of functional mRNA–protein particles requires a plethora of nuclear cotranscriptional and posttranscriptional RNA processing and packaging steps. Faithful execution of these events is closely monitored by surveillance systems that prevent nuclear export of, and/or rapidly degrade, faulty transcripts. Parts of this quality control also serve to eliminate a large number of noncoding RNAs produced by RNA polymerase II. Here, we discuss which aberrant features trigger messenger ribonucleoprotein quality control, how the process is executed, and how it is connected to the transcription machinery and the nuclear pore complex. Content Type Journal ArticleCategory ReviewDOI 10.1007/s00412-008-0166-4Authors Manfred Schmid, University of Aarhus Centre for mR... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1534849 Thu, 19 Jun 2008 07:01:11 +0100 1534849 http://www.medworm.com/index.php?rid=1534851&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F21621556w3k17428%2F Abstract  The meiotic prophase I to metaphase I transition (G2/MI) involves disassembly of synaptonemal complex (SC), chromatin condensation, and final compaction of morphologically distinct MI bivalent chromosomes. Control of these processes is poorly understood. The G2/MI transition was experimentally induced in mouse pachytene spermatocytes by okadaic acid (OA), and kinetic analysis revealed that disassembly of the central element of the SC occurred very rapidly after OA treatment, before histone H3 phosphorylation on Ser10. These events were followed by relocalization of SYCP3 and final condensation of bivalents. Enzymatic control of these G2/MI transition events was studied using small molecule inhibitors: butyrolactone I (BLI), an inhibitor of cyclin-dependent kinases... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1534851 Thu, 19 Jun 2008 07:01:10 +0100 1534851 http://www.medworm.com/index.php?rid=1534850&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fa351218011j8pn66%2F Abstract  The nonrandom positioning of chromosome territories in eukaryotic cells is largely correlated with gene density and is conserved throughout evolution. Gene-rich chromosomes are predominantly central, while gene-poor chromosomes are peripherally localized in interphase nuclei. We previously demonstrated that artificially introduced human chromosomes assume a position equivalent to their endogenous homologues in the diploid colon cancer cell line DLD-1. These chromosomal aneuploidies result in a significant increase in transcript levels, suggesting a relationship between genomic copy number, gene expression, and chromosome position. We previously proposed that each chromosome is marked by a “zip code” that determines its nonrandom position in the nucleus. In thi... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1534850 Thu, 19 Jun 2008 07:01:10 +0100 1534850 http://www.medworm.com/index.php?rid=1517896&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fk1823464w47u3hrk%2F Abstract  Pontin is a multifunctional protein having roles in various cellular processes including regulation of gene expression. Here, we addressed Pontin intracellular localization using two different monoclonal antibodies directed against different Pontin epitopes. For the first time, Pontin was directly visualized in nucleoli where it co-localizes with Upstream Binding Factor and RNA polymerase I. Nucleolar localization of Pontin was confirmed by its detection in nucleolar extracts and by electron microscopy, which revealed Pontin accumulation specifically in the nucleolar fibrillar centers. Pontin localization in the nucleolus was dynamic and Pontin accumulated in large nucleolar dots mainly during S-phase. Pontin concentration in the large nucleolar dots correlated wi... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1517896 Thu, 12 Jun 2008 06:23:32 +0100 1517896 http://www.medworm.com/index.php?rid=1499225&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F327q527778911m43%2F Abstract  Abnormal chromosome segregation at mitosis is one way by which neoplastic cells accumulate the many genetic abnormalities required for tumour development. In this paper, a straightforward morphology-based classification of chromosome segregation errors in cancer is suggested. This classification distinguishes between abnormalities in spindle symmetry (spindle multipolarity, size-asymmetry of ana-telophase poles) and abnormalities in sister chromatid segregation (chromosome bridges, chromatid bridges, chromosome lagging, acentric fragment lagging). Often, these categories of errors must be combined to accurately describe the events in a single abnormal mitotic cell. The suggested categories can to some extent be distinguished by standard chromatin staining. However... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1499225 Thu, 05 Jun 2008 09:52:28 +0100 1499225 http://www.medworm.com/index.php?rid=1493914&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fa57717026545p04m%2F Abstract  Polo-like kinase 1 (Plk1) and Aurora A play key roles in centrosome maturation, spindle assembly, and chromosome segregation during cell division. Here we show that the functions of these kinases during early mitosis are coordinated through Bora, a partner of Aurora A first identified in Drosophila. Depletion of human Bora (hBora) results in spindle defects, accompanied by increased spindle recruitment of Aurora A and its partner TPX2. Conversely, hBora overexpression induces mislocalization of Aurora A and monopolar spindle formation, reminiscent of the phenotype seen in Plk1-depleted cells. Indeed, Plk1 regulates hBora. Following Cdk1-dependent recruitment, Plk1 triggers hBora destruction by phosphorylating a recognition site for $${\text{SCF}}^{{\text{ $ \beta $... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1493914 Tue, 03 Jun 2008 06:18:55 +0100 1493914 http://www.medworm.com/index.php?rid=1466688&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fu7x577g84655v338%2F We report the sequences of two centromere-associated bacterial artificial chromosome clones from a Triticum boeoticum library. Both autonomous and non-autonomous wheat centromeric retrotransposons (CRWs) were identified, both being closely associated with the centromeres of wheat. Fiber-fluorescence in situ hybridization and chromatin immunoprecipitation analysis showed that wheat centromeric retrotransposons (CRWs) represent a dominant component of the wheat centromere and are associated with centromere function. CRW copy number showed variation among different genomes: the D genome chromosomes contained fewer copies than either the A or B genome chromosomes. The frequency of lengthy continuous CRW arrays was higher than that in either rice or maize. The dynamics of CRWs and other retro... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1466688 Thu, 22 May 2008 05:52:04 +0100 1466688 http://www.medworm.com/index.php?rid=1463148&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F5p0u8p77k7466463%2F Abstract  Intercalary heterochromatin consists of extended chromosomal domains which are interspersed throughout the euchromatin and contain silent genetic material. These domains comprise either clusters of functionally unrelated genes or tandem gene duplications and possibly stretches of noncoding sequences. Strong repression of genetic activity means that intercalary heterochromatin displays properties that are normally attributable to classic pericentric heterochromatin: high compaction, late replication and underreplication in polytene chromosomes, and the presence of heterochromatin-specific proteins. Late replication and underreplication occurs when the suppressor of underreplication protein is present in intercalary heterochromatic regions. Intercalary heterochromat... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1463148 Tue, 20 May 2008 06:16:43 +0100 1463148 http://www.medworm.com/index.php?rid=1417392&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fb11t0m2010510765%2F Abstract  Meiotic recombination arises from Rec12/Spo11-dependent formation of DNA double-strand breaks (DSBs) and their subsequent repair. We identified Rec12-binding peaks across the Schizosaccharomyces pombe genome using chromatin immunoprecipitation after reversible formaldehyde cross-linking combined with whole-genome DNA microarrays. Strong Rec12 binding coincided with previously identified DSBs at the recombination hotspots ura4A, mbs1, and mbs2 and correlated with DSB formation at a new site. In addition, Rec12 binding corresponded to eight novel conversion hotspots and correlated with crossover density in segments of chromosome I. Notably, Rec12 binding inversely correlated with guanine–cytosine (GC) content, contrary to findings in Saccharomyces cerevisiae. Althou... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1417392 Thu, 01 May 2008 06:28:09 +0100 1417392 http://www.medworm.com/index.php?rid=1394739&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F56n51432v1984658%2F Abstract  Transcription is a central function occurring in the nucleus of eukaryotic cells in coordination with other nuclear processes. During transcription, the nascent pre-mRNA associates with mRNA-binding proteins and undergoes a series of processing steps, resulting in export-competent mRNA ribonucleoprotein complexes (mRNPs) that are transported into the cytoplasm. Experimental evidence increasingly indicates that the different processing steps (5′-end capping, splicing, 3′-end cleavage) and mRNP export are connected to each other as well as to transcription, both functionally and physically. Here, we review the overall process of mRNP biogenesis with particular emphasis on the functional coupling of transcription with mRNP biogenesis and export and its relationsh... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1394739 Tue, 22 Apr 2008 13:59:44 +0100 1394739 http://www.medworm.com/index.php?rid=1383193&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F73262j802625544g%2F Abstract  In the nuclei of human lymphocytes, chromosome territories are distributed according to the average gene density of each chromosome. However, chromosomes are very heterogeneous in size and base composition, and can contain both very gene-dense and very gene-poor regions. Thus, a precise analysis of chromosome organisation in the nuclei should consider also the distribution of DNA belonging to the chromosomal bands in each chromosome. To improve our understanding of the chromatin organisation, we localised chromosome 7 DNA regions, endowed with different gene densities, in the nuclei of human lymphocytes. Our results showed that this chromosome in cell nuclei is arranged radially with the gene-dense/GC-richest regions exposed towards the nuclear interior and the gen... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1383193 Thu, 17 Apr 2008 15:14:40 +0100 1383193 http://www.medworm.com/index.php?rid=1371593&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Ff822383308617l23%2F Abstract  The human genes CFTR, ASZ1/GASZ, and CTTNBP2/CORTBP2 map to adjacent loci on chromosome 7q31 and display characteristic patterns of nuclear positioning, which strictly correlate with the state of activity. To address the evolutionary conservation of gene positioning, we investigated transcriptional activity and nuclear positioning of the highly conserved murine orthologs and of additional murine genes mapping to the region of conserved synteny on mouse chromosome 6. The results showed that all murine loci investigated constitutively localized in the nuclear interior irrespective of their functional state. Silenced loci did not display preferential association with the nuclear periphery or with chromocenters, respectively, and no differential positioning with respe... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1371593 Sat, 12 Apr 2008 09:28:56 +0100 1371593 http://www.medworm.com/index.php?rid=1345855&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fr23552508447873w%2F Content Type Journal ArticleCategory ErratumDOI 10.1007/s00412-008-0156-6Authors Kazuya Kobayashi, Keio University Department of Biosciences and Informatics Hiyoshi 3-14-1 Kouhoku-ku Yokohama 223-8522 JapanHirotsugu Ishizu, Keio University Department of Biosciences and Informatics Hiyoshi 3-14-1 Kouhoku-ku Yokohama 223-8522 JapanSachiko Arioka, Keio University Department of Biosciences and Informatics Hiyoshi 3-14-1 Kouhoku-ku Yokohama 223-8522 JapanJocelyn Padilla Cabrera, University of the Philippines Institute of Biology Diliman, Quezon City 1101 Manila PhilippinesMotonori Hoshi, Keio University Department of Biosciences and Informatics Hiyoshi 3-14-1 Kouhoku-ku Yokohama 223-8522 JapanMidori Matsumoto, Keio University Department of Biosciences and Informatics Hiyoshi 3-14-1 Kouhoku-... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1345855 Tue, 01 Apr 2008 07:01:29 +0100 1345855 http://www.medworm.com/index.php?rid=1336033&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Ft8697050602tp648%2F Abstract  The centromere is a complex structure required for equal segregation of newly synthesised sister chromatids at mitosis. One of the significant objectives in centromere research is to determine the complete repertoire of protein components that constitute the kinetochore. Here, we identify a novel centromere protein using a centromere-positive autoimmune serum from a patient with watermelon stomach disease. Western blot and screening of a lambda phage expression library revealed a 60-kDa protein, ZNF397. This protein belongs to the classical Cys2His2 group of the zinc-finger protein superfamily and contains two conserved domains: a leucine-rich SCAN domain and nine Cys2His2 zinc fingers. Bioinformatic analysis shows that ZNF397 is conserved in placental mammals. Stab... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1336033 Fri, 28 Mar 2008 08:29:02 +0100 1336033 http://www.medworm.com/index.php?rid=1336034&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F2x64162277544540%2F Abstract  DNA double-strand breaks (DSBs) occur in response to both endogenous and exogenous genotoxic stress. Inappropriate repair of DSBs can lead to either loss of viability or to chromosomal alterations that increase the likelihood of cancer development. In strong support of this assertion, many cancer predisposition syndromes stem from germline mutations in genes involved in DNA DSB repair. Among the most prominent of such tumor suppressor genes are the Breast Cancer 1 and Breast Cancer 2 genes (BRCA1 and BRCA2), which are mutated in familial forms of breast and ovarian cancer. Recent findings implicate BRCA1 as a central component of several distinct macromolecular protein complexes, each dedicated to distinct elements of DNA DSB repair and tumor suppression. Emerging... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1336034 Fri, 28 Mar 2008 08:29:01 +0100 1336034 http://www.medworm.com/index.php?rid=1301554&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fj46230282038131h%2F Abstract  Mre11 is a central factor in creating an optimal substrate for telomerase loading and elongation. We have used a G2/M synchronized telomere-healing assay as a tool to separate different functions of Mre11 that are not apparent in null alleles. An analysis of healing efficiencies of several mre11 alleles revealed that both nuclease and C-terminal mutations led to a loss of healing. Interestingly, trans-complementation of the 49 amino acid C-terminal deletion (ΔC49) and the D16A mutant, deficient in nuclease activity and partially defective in MRX complex formation, restores healing. ΔC49 provokes Rad53 phosphorylation after treatment with the radiomimetic agent MMS exclusively through the Tel1 pathway, suggesting that a Tel1-mediated function is initiated through ... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1301554 Wed, 12 Mar 2008 07:16:39 +0100 1301554 http://www.medworm.com/index.php?rid=1281693&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F6k541g3n8t161438%2F Abstract  To study the correlation of the sequence positions on the physical DNA finger print contig (FPC) map and cytogenetic maps of pachytene and somatic maize chromosomes, sequences located along the chromosome 9 FPC map approximately every 10 Mb were selected to place on maize chromosomes using fluorescent in situ hybridization (FISH). The probes were produced as pooled polymerase chain reaction products based on sequences of genetic markers or repeat-free portions of mapped bacterial artificial chromosome (BAC) clones. Fifteen probes were visualized on chromosome 9. The cytological positions of most sequences correspond on the pachytene, somatic, and FPC maps except some probes at the pericentromeric regions. Because of unequal condensation of mitotic metaphase c... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1281693 Tue, 04 Mar 2008 08:45:15 +0100 1281693 http://www.medworm.com/index.php?rid=1281694&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fm467jr2283407777%2F Abstract  Ordered progression through the cell cycle is essential to maintain genomic stability, and fundamental to this is ubiquitin-mediated proteolysis. In particular, the anaphase-promoting complex/cyclosome (APC/C) ubiquitin ligase destabilises specific regulators at defined times in the cycle to ensure that each round of DNA replication is followed by cell division. Thus, the proper regulation of the APC/C is crucial in each cell cycle. There are several APC/C regulators that restrict its activity to specific cell cycle phases, and amongst these the early mitotic inhibitor 1 (Emi1) protein has recently come to prominence. Emi1 has been proposed to control APC/C in early mitosis; however, recent evidence questions this role. In this review we discuss new evidence that ... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1281694 Tue, 04 Mar 2008 08:45:13 +0100 1281694 http://www.medworm.com/index.php?rid=1257588&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fq6721410m2124757%2F In this study, we describe the cytological behavior of a possible EN component, MRE11, a protein that is important for the repair of the numerous, programmed deoxyribonucleic acid double-strand breaks (DSBs) that occur early in the meiotic prophase. By immunofluorescence, many MRE11 foci were associated with chromosomal axes during early prophase I in both wild-type Arabidopsis and tomato primary microsporocytes. Similar patterns of MRE11 foci were observed in two Arabidopsis mutants (Atspo11-1 and Atprd1) that are defective in DSB formation and synapsis. In tomato chromosomes, MRE11 foci were more common in distal euchromatin than in proximal heterochromatin, consistent with known EN patterns. However, electron microscopic immunogold localization demonstrated that only about 10% of ... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1257588 Fri, 22 Feb 2008 15:53:20 +0100 1257588 http://www.medworm.com/index.php?rid=1236681&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fm278882441q51477%2F Abstract  It has been hypothesized that human clinical neocentromeres and evolutionary novel centromeres (ENC) represent two faces of the same phenomenon. However, there are only two reports of loci harboring both a novel centromere and a clinical neocentromere. We suggest that only the tip of the iceberg has been scratched because most neocentromerization events have a very low chance of being observed. In support of this view, we report here on a neocentromere at 9q33.1 that emerged in a ring chromosome of about 12 Mb. The ring was produced by a balanced rearrangement that was fortuitously discovered because of its malsegregation in the propositus. Chromatin-immunoprecipitation-on-chip experiments using anti-centromere protein (CENP)-A and anti-CENP-C antibodies stro... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1236681 Fri, 15 Feb 2008 18:03:25 +0100 1236681 http://www.medworm.com/index.php?rid=1236682&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fd728757039k6h532%2F In this study, the interaction between CcTopII and CcLim15, especially during catenation, was investigated in detail using atomic force microscopy. We demonstrated earlier that CcLim15 enhanced the catenation activity of CcTopII in a dose-dependent manner. When using two different-sized plasmid rings (5.4 and 3 kbp), which did not have any homologous sequence regions, equal proportions of homologous and heterologous catenanes were produced, suggesting that CcLim15 causes an increase in catenation activity irrespective of the presence of homologous sequences between the rings. We also showed that CcLim15 works as a DNA-condensing agent. Therefore, we speculate that CcLim15 may work as a DNA-condensing factor specific to the zygotene event and that CcTopII is likely to resolve tan... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1236682 Fri, 15 Feb 2008 18:03:24 +0100 1236682 http://www.medworm.com/index.php?rid=1192533&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F8g03n77758745130%2F Abstract  Triploidy has generally been considered to be an evolutionary dead end due to problems of chromosomal pairing and segregation during meiosis. Thus, the formation of tetraploids and diploids from triploid types is a rare phenomenon. In the present study, we demonstrated that inbreeding of the triploid planarian Dugesia ryukyuensis resulted in both diploid and triploid offspring in nature. In the triploids of D. ryukyuensis, chiasmata between homologous chromosomes were observed in both female and male germ lines. This result suggests that both diploid and triploid offspring of this species are produced bisexually by zygotic fusion between sperm and eggs. Hence, this phenomenon may be a novel mechanism in planarian for escaping the triploid state. Content Type Jour... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1192533 Tue, 29 Jan 2008 15:47:35 +0100 1192533 http://www.medworm.com/index.php?rid=1160806&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F90v5p7256628p422%2F Abstract  The chromosomal arrangement of different transgenic repeat arrays inserted at various chromosomal positions was tested by FISH in Arabidopsis 2C leaf and root nuclei. Large lacO (∼10 kb) but not tetO (4.8 kb) or small lacO (∼2 kb) arrays were, in general, more often spatially associated with heterochromatic chromocenters (CC) than flanking regions (that either overlap the array insert position or are between 5 and 163 kb apart from the insert site). Allelic and ectopic pairing frequencies of lacO arrays were significantly increased only in nuclei of lines with two large lacO arrays inserted at different positions on the same chromosome arm. Within the same lines, root nuclei showed a significantly lower increase of pairing frequencies at the ... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1160806 Thu, 17 Jan 2008 15:44:09 +0100 1160806 http://www.medworm.com/index.php?rid=1157928&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F1hg0458643486m12%2F Abstract  In eukaryotes, DNA replication is initiated along each chromosome at multiple sites called replication origins. Locally, each replication origin is “licensed” or specified at the end of the M and the beginning of the G1 phases of the cell cycle. During the S phase when DNA synthesis takes place, origins are activated in stages corresponding to early and late-replicating domains. The staged and progressive activation of replication origins reflects the need to maintain a strict balance between the number of active replication forks and the rate at which DNA synthesis proceeds. This suggests that origin densities (frequency of initiation) and replication fork movement (rates of elongation) must be coregulated to guarantee the efficient and complete duplication o... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1157928 Wed, 16 Jan 2008 15:49:08 +0100 1157928 http://www.medworm.com/index.php?rid=1151970&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F7wl3uw438g7226w3%2F Abstract  Telomere caps prevent chromosome ends from being recognized as DNA double-strand breaks (DSBs). Unlike most organisms studied, the telomere-capping function of Drosophila does not require a specific sequence. Without this sequence component, Drosophila telomeres most resemble DNA breaks and, thus, represent a simpler system for the study of telomere capping. I review recent progress in Drosophila telomere studies, and challenge the notion that Drosophila may not be a relevant model for the study of telomere maintenance. Content Type Journal ArticleCategory ReviewDOI 10.1007/s00412-007-0144-2Authors Yikang S. Rong, National Institutes of Health Laboratory of Biochemistry and Molecular Biology, National Cancer Institute Bethesda Maryland 20892 USA Journal ... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1151970 Mon, 14 Jan 2008 03:46:06 +0100 1151970 http://www.medworm.com/index.php?rid=1149313&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F028086uw825520u3%2F Abstract  Sister chromatid cohesion is a prerequisite for correct segregation and possibly other functions of replicated chromosomes. Except for yeast, no details are known about arrangement of cohesion sites along interphase chromosomes. Within nuclei of several higher plants, sister chromatids are frequently not aligned at various positions along chromosome arms. Therefore, we tested whether preferential alignment positions (“cohesion hot spots”) and constant extension of and distances between aligned sites occur in plants. Along a ~1.2-Mb contig from the bottom arm of chromosome 1, the sister chromatid positions of 13 individual BAC inserts were found to be aligned for ~67–77% of homologues in 4C Arabidopsis thaliana nuclei. The differences between the 13 BAC positi... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1149313 Sat, 12 Jan 2008 16:33:29 +0100 1149313 http://www.medworm.com/index.php?rid=1145240&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F466151501425x762%2F Abstract  Since the original observations made in James German’s Laboratory that Bloom’s syndrome cells lacking BLM exhibit a decreased rate of both DNA chain elongation and maturation of replication intermediates, a large body of evidence has supported the idea that BLM, and other members of the RecQ helicase family to which BLM belongs, play important roles in DNA replication. More recent evidence indicates roles for RecQ helicases in what can broadly be defined as replication fork ‘repair’ processes when, for example, forks encounter lesions or adducts in the template, or when forks stall due to lack of nucleotide precursors. More specifically, several roles in repair of damaged forks via homologous recombination pathways have been proposed. RecQ helicases are ge... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1145240 Fri, 11 Jan 2008 16:23:02 +0100 1145240 http://www.medworm.com/index.php?rid=1111174&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F84476629656jx478%2F We describe the outcome of a comprehensive cytogenetic survey of the common mole-rat, Cryptomys hottentotus, based on G and C banding, fluorescence in situ hybridisation and the analysis of meiotic chromosomes using immunostaining of proteins involved in the formation of synaptonemal complex (SCP1 and SCP3). We identified the presence of a Y-autosome translocation that is responsible for a fixed diploid number difference between males (2n = 53) and females (2n = 54), a character that likely defines the C. hottentotus lineage. Immunostaining, combined with C banding of spermatocytes, revealed a linearised sex trivalent with X1 at one end and X2 at the other, with evidence of reduced recombination between Y and X2 that seems to be heterochromatin dependant in the C. hottentotus lin... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1111174 Thu, 20 Dec 2007 16:24:14 +0100 1111174 http://www.medworm.com/index.php?rid=1096966&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fhh6060738252877m%2F Abstract  Sister chromatids are physically connected by cohesin complexes. This sister chromatid cohesion is essential for the biorientation of chromosomes on the mitotic and meiotic spindle. In many species, cohesion between chromosome arms is partly dissolved in prophase of mitosis, whereas cohesion is protected at centromeres until the onset of anaphase. In vertebrates, the protein Sgo1, protein phosphatase 2A, and several other proteins are required for protection of centromeric cohesin in early mitosis. In fission yeast, the recruitment of heterochromatin protein Swi6/HP1 to centromeres by the histone-methyltransferase Clr4/Suv39h is required for enrichment of cohesin at centromeres already in interphase. We have tested if the Suv39h–HP1 histone methylation pathway i... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1096966 Thu, 13 Dec 2007 17:20:39 +0100 1096966 http://www.medworm.com/index.php?rid=1079234&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F2534162351360860%2F Abstract  Suckling clover, Trifolium dubium Sibth., is a European grassland legume that has spread to many parts of the world. The present work shows that it is an allotetraploid (2n = 4x = 30) combining the genomes of T. campestre Schreb. (2n = 2x = 14) and T. micranthum Viv. (2n = 2x = 16), two diploid species of similar geographic distribution. T. dubium has two nuclear ITS sequences that closely match those of T. campestre and T. micranthum. Genomic in situ hybridisation using genomic DNA of T. campestre and T. micranthum as probes has differentiated the ancestral sets of chromosomes in T. dubium cells. Comparative fluorescence in situ hybridisation analyses of 5S and 18S-26S rDNA loci were also consistent with an allotetraploid structure of the T. d... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1079234 Thu, 06 Dec 2007 16:20:06 +0100 1079234 http://www.medworm.com/index.php?rid=1074235&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F035w3185l36772r3%2F Abstract  Kinetochores bind microtubules laterally in a transient fashion and stably, by insertion of plus ends. These pathways may exist to carry out distinct tasks during different stages of mitosis and likely depend on distinct molecular mechanisms. On isolated chromosomes, we found microtubule nucleation/binding depended additively on both dynein/dynactin and on the Ndc80/Hec1 complex. Studying chromosome movement in living Xenopus cells within the simplified geometry of monopolar spindles, we quantified the relative contributions of dynein/dynactin and the Ndc80/Hec1 complex. Inhibition of dynein/dynactin alone had minor effects but did suppress transient, rapid, poleward movements. In contrast, inhibition of the Ndc80 complex blocked normal end-on attachments of microt... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1074235 Wed, 05 Dec 2007 16:36:37 +0100 1074235 http://www.medworm.com/index.php?rid=1074236&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fbk13014103hhuv11%2F Content Type Journal ArticleCategory Mini-ReviewDOI 10.1007/s00412-007-0138-0Authors Kerry S. Bloom, University of North Carolina at Chapel Hill Department of Biology 623 Fordham Hall CB#3280 Chapel Hill NC 27599–3280 USA Journal ChromosomaOnline ISSN 1432-0886Print ISSN 0009-5915 (Source: Chromosoma) Chromosoma journals http://www.medworm.com/rss/comments.php?id=1074236 Mon, 03 Dec 2007 18:16:09 +0100 1074236 http://www.medworm.com/index.php?rid=1062309&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fw761805326r22w52%2F Abstract  Semiconductor nanocrystals, also called quantum dots (QDs), are novel inorganic fluorophores which are brighter and more photostable than organic fluorophores. In the present study, highly dispersive QD-labeled oligonucleotide (TAG)8 (QD-deoxyribonucleic acid [DNA]) conjugates were constructed via the metal-thiol bond, which can be used as fluorescence in situ hybridization (FISH) probes. FISH analysis of maize metaphase chromosomes using the QD-DNA probes showed that the probes could penetrate maize chromosomes and nuclei and solely hybridized to complementary target DNAs. Compared with the conventional organic dyes such as Cy3 and fluorescein isothiocyanate, this class of luminescent labels bound with oligonucleotides is brighter and more stable against photoblea... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1062309 Thu, 29 Nov 2007 16:39:00 +0100 1062309 http://www.medworm.com/index.php?rid=1062308&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fm7t6k27p2211625k%2F Abstract  Conjugation of SUMO to target proteins is an essential eukaryotic regulatory pathway. Multiple potential SUMO substrates were identified among nuclear and chromatin proteins by proteomic approaches. However, the functional roles of SUMO-modified pools of individual proteins remain largely obscure, as only a small fraction of a given target is sumoylated and therefore is experimentally inaccessible. To overcome this technical difficulty in case of Topoisomerase II, we employed constitutive SUMO modification, enabling tracking of modified Top2p, not only biochemically but also cytologically and genetically. Topoisomerase II fused to a critical number of SUMO repeats is concentrated at the specific intranuclear domain, the nucleolus, when more than four SUMO moieties... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1062308 Thu, 29 Nov 2007 16:39:00 +0100 1062308 http://www.medworm.com/index.php?rid=1026671&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fg801m7834672q42g%2F In this study, we investigated the effects of sodium arsenite (NaAsO2) on global histone modifications and nucleosome-associated proteins. Our findings revealed that NaAsO2 exposure significantly increases global histone acetylation. This effect was related to the inhibition of histone deacetylase (HDAC) activity because NaAsO2 was able to inhibit HDACs comparable to the well-known HDAC inhibitor trichostatin A (TSA). Furthermore, analyses of the dynamic properties of the nucleosome-associated high mobility group N proteins demonstrate that NaAsO2 elevates their mobility. Thus, our data suggest that NaAsO2 induces chromatin opening by histone hyperacetylation due to HDAC inhibition and increase of the mobility of nucleosome-associated proteins. As the chromatin compaction is crucial fo... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1026671 Tue, 13 Nov 2007 16:12:08 +0100 1026671 http://www.medworm.com/index.php?rid=1023991&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fd521r472p4293x7w%2F Abstract  There is ample evidence that the enhancers of a promoterless yellow locus in one homologous chromosome can activate the yellow promoter in the other chromosome where the enhancers are inactive or deleted, which is indicative of a high specificity of the enhancer–promoter interaction in yellow. In this paper, we have found that the yellow sequence from −100 to −69 is essential for stimulation of the heterologous eve (TATA-containing) and white (TATA-less) promoters by the yellow enhancers from a distance. However, the presence of this sequence is not required when the yellow enhancers are directly fused to the heterologous promoters or are activated by the yeast GAL4 activator. Unexpectedly, the same promoter proximal region defines previously described promoter-... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1023991 Mon, 12 Nov 2007 08:21:43 +0100 1023991 http://www.medworm.com/index.php?rid=1016844&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fc62417414881l3j3%2F Abstract  PICH (Plk1-interacting checkpoint helicase) was recently identified as an essential component of the spindle assembly checkpoint and shown to localize to kinetochores, inner centromeres, and thin threads connecting separating chromosomes even during anaphase. In this paper, we have used immuno-fiber fluorescence in situ hybridization and chromatin-immunoprecipitation to demonstrate that PICH associates with centromeric chromatin during anaphase. Furthermore, by careful analysis of PICH-positive anaphase threads through FISH as well as bromo-deoxyurdine and CREST labeling, we strengthen the evidence that these threads comprise mainly alphoid centromere deoxyribonucleic acid. Finally, by timing the addition of ICRF-193 (a specific inhibitor of topoisomerase-II alpha... Chromosoma journals http://www.medworm.com/rss/comments.php?id=1016844 Thu, 08 Nov 2007 16:08:36 +0100 1016844 http://www.medworm.com/index.php?rid=998166&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Ftp35qx98835u4070%2F Abstract  The zebra finch (Taeniopygia guttata) has a large Z chromosome and highly condensed W chromosome. We used the random amplified polymorphic DNA (RAPD) polymerase chain reaction (PCR) technique to isolate female-specific sequences ZBM1 and ZBM2. Southern blot hybridization to male and female zebra finch genomic DNA suggested that these sequences were located on the W chromosome, although homologous sequences appeared to be autosomal or Z-linked. Fluorescent in situ hybridization (FISH) using bacterial artificial chromosome (BAC) clones corresponding to ZBM sequences showed hybridization to the whole W chromosome, suggesting that the BACs encode sequences that are repeated across the entire W chromosome. Based on the sequencing of a ZBM repetitive sequence and Z chrom... Chromosoma journals http://www.medworm.com/rss/comments.php?id=998166 Wed, 31 Oct 2007 14:45:11 +0100 998166 http://www.medworm.com/index.php?rid=994492&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fu436750938451h8n%2F Abstract  The synaptonemal complex (SC) is an evolutionarily conserved structure that mediates synapsis of homologous chromosomes during meiotic prophase I. Previous studies have established that the chromatin of homologous chromosomes is organized in loops that are attached to the lateral elements (LEs) of the SC. The characterization of the genomic sequences associated with LEs of the SC represents an important step toward understanding meiotic chromosome organization and function. To isolate these genomic sequences, we performed chromatin immunoprecipitation assays in rat spermatocytes using an antibody against SYCP3, a major structural component of the LEs of the SC. Our results demonstrated the reproducible and exclusive isolation of repeat deoxyribonucleic acid (DNA) ... Chromosoma journals http://www.medworm.com/rss/comments.php?id=994492 Tue, 30 Oct 2007 14:43:26 +0100 994492 http://www.medworm.com/index.php?rid=991256&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fh15264x52223316n%2F Abstract  The cohesin complex is a chromosomal component required for sister chromatid cohesion that is conserved from yeast to man. The similarly conserved Nipped-B protein is needed for cohesin to bind to chromosomes. In higher organisms, Nipped-B and cohesin regulate gene expression and development by unknown mechanisms. Using chromatin immunoprecipitation, we find that Nipped-B and cohesin bind to the same sites throughout the entire non-repetitive Drosophila genome. They preferentially bind transcribed regions and overlap with RNA polymerase II. This contrasts sharply with yeast, where cohesin binds almost exclusively between genes. Differences in cohesin and Nipped-B binding between Drosophila cell lines often correlate with differences in gene expression. For example, ... Chromosoma journals http://www.medworm.com/rss/comments.php?id=991256 Sat, 27 Oct 2007 17:34:31 +0100 991256 http://www.medworm.com/index.php?rid=963927&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fm2774h6246200405%2F Abstract  Highly phosphorylated, soluble inositides are an emerging family of potential eukaryotic second messengers. The mechanisms for generating an outstanding diversity of mono- and pyrophosphorylated inositides have been recently elucidated and require a series of conserved lipases, kinases, and phosphatases. With several of the inositol kinases and the phospholipase C having access to the nucleus, roles for inositides in nuclear functions have been suggested. In support of this hypothesis, multiple studies have revealed the protein machines that are modulated by these inositides and found specific roles in nuclear physiology. In this paper, we review a novel paradigm for regulating gene expression at distinct steps by different inositide isomers. We discuss discoverie... Chromosoma journals http://www.medworm.com/rss/comments.php?id=963927 Thu, 18 Oct 2007 16:14:58 +0100 963927 http://www.medworm.com/index.php?rid=955711&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F47tk591g125t6vt6%2F Abstract  The packing of mammalian DNA into chromatin plays an important role in cell differentiation and selection of epigenetically marked genes for expression or silencing. The first level of folding, the nucleosome, is evolutionary conserved. It allows transcription, after remodeling and/or histone modifications. The second level, the transcriptionally dormant 30 nm fibre, exhibits species and tissue variations in the chromatin repeat length. Nevertheless, very similar structures of fibres have been observed in all metazoans, and therefore, have to accommodate variable linker lengths with a corresponding change of tilt of the nucleosomes, which is defined by the DNA helical periodicity. So far, none of the models for a regular fibre structure has considered this re... Chromosoma journals http://www.medworm.com/rss/comments.php?id=955711 Sat, 13 Oct 2007 17:13:33 +0100 955711 http://www.medworm.com/index.php?rid=930047&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F63861x622n152315%2F Abstract   Drosophila Nipped-B is an essential protein that has multiple functions. It facilitates expression of homeobox genes and is also required for sister chromatid cohesion. Nipped-B is conserved from yeast to man, and its orthologs also play roles in deoxyribonucleic acid repair and meiosis. Mutation of the human ortholog, Nipped-B-Like (NIPBL), causes Cornelia de Lange syndrome (CdLS), associated with multiple developmental defects. The Nipped-B protein family is required for the cohesin complex that mediates sister chromatid cohesion to bind to chromosomes. A key question, therefore, is whether the Nipped-B family regulates gene expression, meiosis, and development by controlling cohesin. To gain insights into Nipped-B’s functions, we compared the effects of sev... Chromosoma journals http://www.medworm.com/rss/comments.php?id=930047 Tue, 02 Oct 2007 16:12:59 +0100 930047 http://www.medworm.com/index.php?rid=887669&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fk3446632957r8446%2F Abstract  In Drosophila melanogaster, broken chromosome ends behave as real telomeres and are believed to be covered with telomere-specific chromatin. It has been shown previously that the telomeric chromatin represses normal activity of enhancers that regulate yellow expression in wings and body cuticle. In this paper, we have found that a modified yellow promoter is fully active in the wing and body cuticle when it is located at the chromosome end, which is evidence that the telomeric chromatin does not repress transcription. Substitution of the yellow core promoter region, including TATA and Inr, with the promoter regions of the eve, hsp70 (TATA-containing), and white (TATA-less) promoters does not affect the ability of the promoter to be cis- or trans-activated by the yello... Chromosoma journals http://www.medworm.com/rss/comments.php?id=887669 Tue, 18 Sep 2007 19:38:40 +0100 887669 http://www.medworm.com/index.php?rid=852884&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fc03p41x377888568%2F Abstract  In Drosophila, the Polycomb group and trithorax group proteins play a critical role in controlling the expression states of homeotic gene complexes during development. The common view is that these two classes of proteins bind to the homeotic complexes and regulate transcription at the level of chromatin. In the present work, we tested the involvement of both groups in mitotic heterochromatin formation in Drosophila. Using specific antibodies, we show that some of the tested Pc-G proteins are present in heterochromatin, while all the tested trx-G proteins localize to specific regions of heterochromatin in both mitotic chromosomes and interphase nuclei. We also observed that mutations in trx-G genes are recessive enhancers of position-effect variegation and are able... Chromosoma journals http://www.medworm.com/rss/comments.php?id=852884 Fri, 07 Sep 2007 21:50:03 +0100 852884 http://www.medworm.com/index.php?rid=845416&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F2112k5660q44v537%2F Content TypeJournal Article JournalChromosomaOnline ISSN 1432-0886Print ISSN 0009-5915 (Source: Chromosoma) Chromosoma journals http://www.medworm.com/rss/comments.php?id=845416 Wed, 05 Sep 2007 07:04:45 +0100 845416 http://www.medworm.com/index.php?rid=841369&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fx3t2411860289464%2F Abstract  The ring-shaped cohesin complex links sister chromatids until their timely segregation during mitosis. Cohesin is enriched at centromeres where it provides the cohesive counterforce to bipolar tension produced by the mitotic spindle. As a consequence of spindle tension, centromeric sequences transiently split in pre-anaphase cells, in some organisms up to several micrometers. This ‘centromere breathing’ presents a paradox, how sister sequences separate where cohesin is most enriched. We now show that in the budding yeast Saccharomyces cerevisiae, cohesin binding diminishes over centromeric sequences that split during breathing. We see no evidence for cohesin translocation to surrounding sequences, suggesting that cohesin is removed from centromeres during breat... Chromosoma journals http://www.medworm.com/rss/comments.php?id=841369 Tue, 04 Sep 2007 14:48:45 +0100 841369 http://www.medworm.com/index.php?rid=841368&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fn2538q7m7185n277%2F Abstract  The X family DNA polymerases λ (CcPolλ) and μ (CcPolμ) were shown to be expressed during meiotic prophase in the basidiomycete, Coprinus cinereus. These two polymerases are the only members of the X family in the C. cinereus genome. The open reading frame of CcPolλ encoded a predicted product of 800 amino acid residues and that of CcPolμ of 621 amino acid residues. Both CcPolλ and CcPolμ required Mn2+ ions for activity, and both were strongly inhibited by dideoxythymidine triphosphate. Unlike their mammalian counterparts, CcPolλ and CcPolμ had no terminal deoxynucleotidyl transferase activity. Immunostaining analysis revealed that CcPolλ was present at meiotic prophase nuclei in zygotene and pachytene cells, which is the period when homologous chromosomes p... Chromosoma journals http://www.medworm.com/rss/comments.php?id=841368 Tue, 04 Sep 2007 14:48:45 +0100 841368 http://www.medworm.com/index.php?rid=841367&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Feuh7462700181vx1%2F Abstract  After applying proper deoxyribonucleic acid (DNA) probes, fluorescence in situ hybridization (FISH) showed that the 8/9 centromeres—one per chromatid of the male haploid complement (X0) of Pyrgomorpha conica grasshopper—colocalized at the spermatid blunt end, where the spermatozoa flagellum inserts. A bundle of aligned 4′,6-diamidino-2-phenylindole-positive chromatid scaffolds, which formed the central spermatid core, was observed after DNA breakage detection followed by FISH. Modular nature of scaffold DNA was occasionally evident. The technique also showed that in the early spermatid, the chromatid scaffolds lacked any DNA nick, whereas abundant breaks accumulated in the surrounding loops. Moreover, immunodetection showed that scaffold DNA participated in t... Chromosoma journals http://www.medworm.com/rss/comments.php?id=841367 Tue, 04 Sep 2007 14:48:45 +0100 841367 http://www.medworm.com/index.php?rid=830686&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Frm382h77q70w3nw2%2F Abstract  Telomeres, the terminal chromosomal structure crucial for maintaining genomic integrity, shorten with deoxyribonucleic acid replications in most human somatic cells. Chromosomes carrying critically short telomeres tend to form end-to-end fusions, which are subject to breakage during cell division. However, it remains obscure how such telomere-mediated fusions are resolved during the process of immortalization, which is an early and indispensable step toward cancer. It has been hypothesized that the breakage could occur at either the microtubule or chromatid, causing numerical or structural chromosome instability, respectively. In this paper, we show that although the distributions of chromosomal segment losses or gains involved in structural aberrations were signi... Chromosoma journals http://www.medworm.com/rss/comments.php?id=830686 Wed, 29 Aug 2007 07:03:56 +0100 830686 http://www.medworm.com/index.php?rid=744390&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fet8112481h3ug3h8%2F In this study, we highlight another way of moving chromosomes remotely from outside the nucleus, which involves SUN and KASH domain nuclear envelope proteins. SUN and KASH domain protein families are known to connect the nucleus to cytoskeletal networks and play a role in migration and positioning of the nucleus. Recent studies in the fission yeast Schizossacharomyces pombe demonstrated an additional role for the SUN–KASH protein complex in chromosome movements. During meiotic prophase, telomeres are moved to rearrange chromosomes within the nucleus. The SUN–KASH protein complex located in the nuclear envelope is involved in this process. Telomeres are connected to the SUN protein on the nucleoplasmic side, and the dynein motor complex binds to the KASH protein on the cytoplasmic... Chromosoma journals http://www.medworm.com/rss/comments.php?id=744390 Wed, 18 Jul 2007 06:47:36 +0100 744390 http://www.medworm.com/index.php?rid=729468&cid=s_33449_176_f&fid=33449&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fg6n915472n474m2w%2F Abstract  The chromosomal distribution of 41-bp repeats, known as CNM and PO41 repeats in the chicken genome and BglII repeats in the Japanese quail, was analyzed precisely using giant lampbrush chromosomes (LBC) from chicken, Japanese quail, and turkey growing oocytes. The PO41 repeat is conserved in all galliform species, whereas the other repeats are species specific. In chicken and quail, the centromere and subtelomere regions share homologous satellite sequences. RNA polymerase II transcribes the 41-bp repeats in both centromere and subtelomere regions. Ongoing transcription of these repeats was demonstrated by incorporation of BrUTP injected into oocytes at the lampbrush stage. RNA complementary to both strands of CNM and PO41 repeats is present on chicken LBC loops, w... Chromosoma journals http://www.medworm.com/rss/comments.php?id=729468 Tue, 10 Jul 2007 07:18:41 +0100 729468