Macrotenes Chromosomes
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REPOSITORIES: ENA
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Project description:The three-dimensional organization of chromosomes can have a profound impact on their replication and expression. The chromosomes of higher eukaryotes possess discrete compartments that are characterized by differing transcriptional activities. Contrastingly, most bacterial chromosomes have simpler organization with local domains, the boundaries of which are influenced by gene expression. Numerous studies have revealed that the higher-order architectures of bacterial and eukaryotic chromosomes are dependent on the actions of Structural Maintenance of Chromosomes (SMC) superfamily protein complexes, in particular the near-universal condensin complex. Intriguingly, however, many archaea, including members of the genus Sulfolobus do not encode canonical condensin. We describe chromosome conformation capture experiments on Sulfolobus species. These reveal the presence of distinct domains along Sulfolobus chromosomes that undergo discrete and specific higher-order interactions, thus defining two compartment types. We observe causal linkages between compartment identity, gene expression and binding of a hitherto uncharacterized SMC superfamily protein that we term “coalescin”.
2019-09-19 | GSE128063 | GEO
Project description:The duplication and segregation of chromosomes involve the dynamic re-organization of their internal structure by conserved architectural proteins, such as structural maintenance of chromosomes complexes (i.e., cohesin and condensin). Although the roles of these factors is actively investigated, a genome-wide view of chromosome dynamic architecture at both small and large-scales during cell division remains elusive. Here we report the first comprehensive 4D analysis of the Saccharomyces cerevisiae genome higher-order organization during the cell cycle, and investigate the roles of SMC in the observed structural transitions. During replication, cohesion establishment promotes long-range intra-chromosomal contacts and correlates with the individualization of chromosomes, which culminates at metaphase. Mitotic chromosomes are then abruptly reorganized in anaphase by mechanical forces exerted by the mitotic spindle. The formation of a condensin-dependent loop, that bridges the centromere cluster with the rDNA loci, suggests that condensin-mediated forces may also directly facilitate segregation. This work provides a comprehensive overview of chromosome dynamics during the cell cycle of a unicellular eukaryote that recapitulates and unveils new features of highly conserved stages of the cell division.
2017-07-20 | GSE90902 | GEO
Project description:X chromosome inactivation (XCI) is a dosage compensation mechanism that silences the majority of genes on one X chromosome in each female cell. In order to characterize epigenetic changes that accompany this process, we measured DNA methylation levels in both 45,X Turner syndrome patients, who carry a single active X chromosome (Xa) and normal 46,XX females, who carry one Xa and one inactive X (Xi). Methylated DNA was immunoprecipitated and hybridized to tiling oligonucleotide arrays, generating epigenetic profiles of active and inactive X chromosomes. We observed that XCI is accompanied by changes in DNA methylation specifically at CpG islands. While the majority of CpG islands show increased methylation levels on the Xi, XCI results in reduced methylation at ~20% of CpG islands. Both intra- and inter-genic CpG islands are epigenetically modified, with the biggest increase in methylation occuring at the promoters of genes silenced by XCI. In contrast, genes escaping XCI have low levels of promoter methylation, while genes that undergo polymorphic silencing show intermediate increases in methylation proportionate to their frequency of inactivation. Thus promoter methylation and susceptibility to XCI are correlated. We observed a global correlation between CpG island methylation and the evolutionary age of different X chromosome strata, and that genes escaping XCI show increased methylation within gene bodies. We utilized our epigenetic map to predict both novel genes escaping XCI, and to identify sequence features that may contribute to the XCI process. Finally, as our study included Turner syndrome patients with single X chromosomes of both maternal and paternal origin we searched for parent-of-origin specific methylation differences, but found no evidence to support imprinting on the human X chromosome. Our study provides the first epigenetic profile of active and inactive X chromosomes, giving novel insights into the phenomenon of dosage compensation. Methylated DNA was enriched by immunoprecipitation using antibodies against 5-methylcytosine. meDIP and input DNA was labeled with cy5 and cy3 respectively and hybridized to Nimblegen arrays comprising 2.1 million 50-85mers covering human chromosomes 20, 21, 22, X and Y at a mean density of ~1 probe per 100bp. Resulting log2 fluorescence ratios correspond to methylation levels. Seven patients with Turner syndrome (45,X karyotype), and three normal females (46,XX karyotype) were analyzed. Of the Turner syndrome cases, four had a maternally-derived X, and three had a paternally-derived X chromosome.
2010-07-20 | E-GEOD-22551 | biostudies-arrayexpress
Project description:X chromosome inactivation (XCI) is a dosage compensation mechanism that silences the majority of genes on one X chromosome in each female cell. In order to characterize epigenetic changes that accompany this process, we measured DNA methylation levels in both 45,X Turner syndrome patients, who carry a single active X chromosome (Xa) and normal 46,XX females, who carry one Xa and one inactive X (Xi). Methylated DNA was immunoprecipitated and hybridized to tiling oligonucleotide arrays, generating epigenetic profiles of active and inactive X chromosomes. We observed that XCI is accompanied by changes in DNA methylation specifically at CpG islands. While the majority of CpG islands show increased methylation levels on the Xi, XCI results in reduced methylation at ~20% of CpG islands. Both intra- and inter-genic CpG islands are epigenetically modified, with the biggest increase in methylation occuring at the promoters of genes silenced by XCI. In contrast, genes escaping XCI have low levels of promoter methylation, while genes that undergo polymorphic silencing show intermediate increases in methylation proportionate to their frequency of inactivation. Thus promoter methylation and susceptibility to XCI are correlated. We observed a global correlation between CpG island methylation and the evolutionary age of different X chromosome strata, and that genes escaping XCI show increased methylation within gene bodies. We utilized our epigenetic map to predict both novel genes escaping XCI, and to identify sequence features that may contribute to the XCI process. Finally, as our study included Turner syndrome patients with single X chromosomes of both maternal and paternal origin we searched for parent-of-origin specific methylation differences, but found no evidence to support imprinting on the human X chromosome. Our study provides the first epigenetic profile of active and inactive X chromosomes, giving novel insights into the phenomenon of dosage compensation.
2010-07-20 | GSE22551 | GEO
Project description:The somatic macronucleus (MAC) and germline micronucleus (MIC) of Tetrahymena thermophila differ in chromosome numbers, sizes, functions, transcriptional activities, and cohesin complex location. However, the higher-order chromatin organization in T. thermophila which contains both cohesin free MAC and cohesin located MIC are largely unknown. Here, we examined the higher-order chromatin organization in the two distinct nuclei of T. thermophila using the Hi-C and HiChIP. Interestingly, we found that the crescent MIC possess specific chromosome interaction pattern. All the telomeres or centromeres on the five MIC chromosomes clustering together, respectively, which could help to identify the midpoints of centromeres in the MIC. We found the transcriptionally active MAC chromosomes lack A/B compartments, topologically associating domains (TADs) and chromatin loops. The transcriptionally inert MIC chromosomes also without A/B compartments and chromatin loops, but have TAD-like structures. The boundaries of the TAD-like structures in the MIC were highly consistent with the chromatin breakage sequence (CBS) sites, suggesting that each TAD-like structure of the MIC chromosomes develops into one MAC chromosome during MAC development during conjugation. Overall, we revealed the higher-order chromatin organization in the T. thermophila and found the chromatin structures might play important roles during the development of the MAC chromosomes.
2020-02-21 | GSE140429 | GEO
Project description:Cohesin holds sister chromatids together to enable their accurate segregation in mitosis. How, and where, cohesin binds to chromosomes are still poorly understood, and recent genome-wide surveys have revealed an apparent disparity between its chromosomal association patterns in different organisms. Here, we present the high-resolution analysis of cohesin localisation along fission yeast chromosomes. This reveals that several determinants, thought specific for distinct organisms, come together to shape the overall distribution. Cohesin is detected at chromosomal loading sites, characterised by the cohesin loader Mis4/Ssl3, in regions of strong transcriptional activity. Cohesin also responds to transcription by downstream translocation and accumulation at convergent transcriptional terminators surrounding the loading sites. As cells enter mitosis, a fraction of cohesin leaves chromosomes in a cleavage-independent reaction, while a substantial pool of cohesin dissociates when it is cleaved at anaphase onset. As a unique feature, centromeric cohesin spreads out onto chromosome arms during mitosis as the heterochromatin protein Swi6 dissociates from centromeres. Together, this allows us to suggest conserved mechanisms for chromosomal cohesin binding in eukaryotes.
2008-12-31 | GSE13517 | GEO
Project description:The dataset is a concatenation of nanoLC-MS/MS analyses performed on different sample types/sample preparations of human proteins on various instrumental platforms in the laboratory. A franco-swiss collaboration to identify missing human proteins on chromosomes 2 and 14 in the frame of the Human Proteome Project, set up a bioinformatic screen over all datasets accumulated in the laboratory in order to detect proteins classified as “missing” by NextProt.
2016-10-21 | MSV000080273 | MassIVE
Project description:Histone modifications represent one of the key factors contributing to proper genome regulation. One of the histone modifications involved in gene silencing is H3K9 methylation, which is found in the chromosomes across different eukaryotes and controlled by SU(VAR)3-9 and its orthologs. Although SU(VAR)3-9 was discovered over two decades ago, little is known about the details of its chromosomal distribution pattern. To fill in this gap, we used DamID-seq approach and obtained high-resolution genome-wide profiles for SU(VAR)3-9 in two somatic and two germline tissues of fruitfly.
2017-04-04 | GSE97351 | GEO
Project description:Faithful meiotic chromosome inheritance and fertility relies on the stimulation of meiotic crossover recombination by potentially genotoxic DNA double-strand breaks (DSBs). To avoid excessive damage, feedback mechanisms down-regulate DSBs on chromosomes that have successfully initiated crossover repair. In Saccharomyces cerevisiae, this regulation requires the removal of the conserved DSB-promoting protein Hop1/HORMAD during chromosome synapsis. Here, we identify privileged end-adjacent regions (EARs) spanning roughly 100 Kb near all telomeres that escape DSB downregulation. These regions retain Hop1 and continue to break in pachynema despite normal synaptonemal complex deposition. Differential retention of Hop1 requires the disassemblase Pch2/TRIP13, which preferentially removes Hop1 from telomere-distant sequences, and is modulated by the histone deacetylase Sir2 and the nucleoporin Nup2. Importantly, the uniform size of EARs among chromosomes contributes to disproportionately high DSB and repair signals on short chromosomes in pachynema, suggesting that EARs partially underlie the curiously high recombination rate of short chromosomes. Grant ID: Research grant #6-FY16-208 Grant title: Meiotic segregation of small chromosomes Funding Source: March of Dimes Foundation Affiliation: NEW YORK UNIVERSITY Name: Andreas Hochwagen
2019-01-10 | GSE105111 | GEO