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Systematic identification of factors bound to isolated metaphase ESC chromosomes reveals a role for chromatin repressors in compaction

ABSTRACT: Epigenetic information is transmitted from mother to daughter cells through mitosis. To identify trans-acting factors and cis-acting elements that might be important for conveying epigenetic memory through cell division, we isolated native (unfixed) chromosomes from metaphase-arrested cells using flow cytometry and performed LC-MS/MS to determine the repertoire of chromosome-bound proteins. Quantitative proteomic comparisons between metaphase-arrested cell lysates and chromosome-sorted samples revealed a cohort of proteins that were significantly enriched on mitotic ESC chromosomes. These include pluripotency-associated transcription factors, repressive chromatin-modifiers (such as PRC2 and DNA methyl-transferases) and proteins governing chromosome architecture. We showed that deletion of PRC2, DNMT1/3a/3b or Mecp2 provoked an increase in the size of individual mitotic chromosomes consistent with de-condensation, as did experimental cleavage of cohesin complexes. These data provide a comprehensive inventory of chromosome-bound factors in pluripotent stem cells at mitosis and reveal an unexpected role for chromatin repressor complexes in preserving mitotic chromosome compaction.

ORGANISM(S): Mus musculus

PROVIDER: GSE136681 | GEO | 2020/06/01

REPOSITORIES: GEO

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Analysis of factors bound to native metaphase ESC chromosomes following purification by flow cytometry

Project description:Stem cells are able to self-renew and also generate differentiated progeny. How gene expression patterns are transmitted through mitosis remains unresolved. Conventional studies have relied upon rigorous cell-cycle-stage synchronisation to find factors in mitotic lysates that could ‘bookmark’ the genome. Here we use an alternative approach, purifying native-unfixed mitotic chromosomes from different cell types using flow cytometry and directly identifying chromosome-bound proteins by LC-MS/MS. This revealed a rich profile of pluripotency- and lineage-specific transcription factors that remained bound to mitotic chromosomes in pluripotent ESCs and lymphocytes, as well as factors implicated in chromosome condensation, architecture and gene silencing. Removal of DNA methylation, PRC2 activity, or in situ cleavage of cohesin, each resulted in the reduced compaction of mitotic chromosomes. These data provide a comprehensive catalogue of bookmarking factors in pluripotent versus lineage-restricted cells and demonstrate an expected duality of function by candidates in regulating both gene expression and mitotic chromosome structure.

2020-06-15 | PXD015251 | Pride

Proteomics profiling of mitotic arrest by transcriptional silencing of the Cdc20 homolog slp1 in fission yeast

Project description:Depletion of the APC/C activator Cdc20 arrests cells in metaphase with high levels of the mitotic cyclin (Cyclin B) and the Separase inhibitor Securin. In mammalian cells this arrest has been exploited for the treatment of cancer with drugs that engage the spindle assembly checkpoint and, recently, with chemical inhibitors of the APC/C. While most cells arrested in mitosis for prolonged periods undergo apoptosis, others skip cytokinesis and enter G1 with unsegregated chromosomes. This process, known as mitotic slippage, generates aneuploidy and increases genomic instability in the cancer cell. Here, we analyse the behaviour of fission yeast cells arrested in mitosis through the transcriptional silencing of the Cdc20 homolog slp1. While depletion of slp1 readily halts cells in metaphase, this arrest is only transient and a majority of cells eventually undergo cytokinesis and show steady mitotic dephosphorylation. As a result, we generated this label-free dataset with the aim of providing further insights into the global dynamics of protein expression under slp1 depletion and the underlying mechanisms that contribute to the mitotic escape.

2022-10-13 | PXD031975 | Pride

IDENTIFICATION OF SUMO-2/3 MODIFIED PROTEINS ASSOCIATED WITH MITOTIC CHROMOSOMES

Project description:Sumoylation is essential for progression through mitosis, but the specific protein targets and functions remain poorly understood. In this study, we used chromosome spreads to more precisely define the localization of SUMO-2/3 to the inner-centromere and protein scaffold of mitotic chromosomes. We also developed methods to immune-purify proteins modified by endogenous, untagged SUMO-2/3 from mitotic chromosomes. Using these methods we identified 149 chromosome associated SUMO-2/3 substrates by nLC-ESI-MS/MS. Approximately one-third of the identified proteins have reported functions in mitosis. Consistent with SUMO-2/3 immunolocalization, we identified known centromere and kinetochore associated proteins, as well as chromosome scaffold associated proteins. Notably, >30 proteins involved in chromatin modification or remodeling were identified. Our results provide insights into the roles of sumoylation as a regulator of chromatin structure and other diverse processes in mitosis. Furthermore, our purification and fractionation methodologies represent an important compliment to existing approaches to identify sumoylated proteins using exogenously expressed and tagged SUMOs.

2014-10-07 | MSV000078890 | MassIVE

Budding yeast Wapl controls sister chromatid cohesion maintenance and the chromosome condensation status [PK-ChIP]

Project description:Cohesin acetylation by Eco1 during DNA replication establishes sister chromatid cohesion. We show that acetylation makes cohesin resistant to Wapl activity from S-phase until mitosis. Wapl turns out to be a key regulator of cohesin dynamics on chromosomes by controling cohesin maintenance following its establishment in S-phase and its role in chromosome condensation. The Affymetrix Saccharomyces cerevisiae Chip Tiling 1.0R Arrays were used to analyze the binding pattern of Scc1 along the genome of Saccharomyces cerevisiae in late G1 and metaphase arrested cells.

2012-11-22 | E-GEOD-42457 | biostudies-arrayexpress

Loss of H3K9 tri-methylation alters mitotic chromosome compaction and transcription factor retention during mitosis

Project description:Recent studies have shown that repressive chromatin machinery, including DNA methyltransferases (DNMTs) and Polycomb Repressor Complexes (PRCs), bind to chromosomes throughout mitosis and their depletion results in increased chromosome size. Enzymes that catalyse H3K9 methylation, such as Suv39h1, Suv39h2, G9a, GLP are also retained by mitotic chromosomes. Surprisingly however, mutants lacking H3K9me3 have unusually small and compact mitotic chromosomes that are associated with increased H3S10ph and H3K27me3 levels. Chromosome size and centromere compaction in these mutants was rescued by providing exogenous Suv39h1, or inhibiting Ezh2 activity. Quantitative proteomic comparisons of native mitotic chromosomes isolated from wildtype versus Suv39h1,2 double null ESCs revealed that H3K9me3 was essential for the efficient retention of bookmarking factors such as Esrrb. These results highlight an unexpected role for repressive heterochromatin domains in preserving transcription factor binding through mitosis, and underscore the importance of H3K9me3 for sustaining chromosome architecture and epigenetic memory during cell division.

2022-10-12 | PXD030771 | Pride

Loss of H3K9 tri-methylation alters chromosome compaction and transcription factor retention during mitosis

Project description:Recent studies have shown that repressive chromatin machinery, including DNA methyltransferases and Polycomb Repressor Complexes, bind to chromosomes throughout mitosis and their depletion results in increased chromosome size. Here we show that enzymes that catalyse H3K9 methylation, such as Suv39h1, Suv39h2, G9a and Glp, are also retained on mitotic chromosomes. Surprisingly however, mutants lacking H3K9me3 have unusually small and compact mitotic chromosomes associated with increased H3S10ph and H3K27me3 levels. Chromosome size and centromere compaction in these mutants were rescued by providing exogenous Suv39h1, or inhibiting Ezh2 activity. Quantitative proteomic comparisons of native mitotic chromosomes isolated from wildtype versus Suv39h1/Suv39h2 double-null mouse ESCs revealed that H3K9me3 was essential for the efficient retention of bookmarking factors such as Esrrb. These results highlight an unexpected role for repressive heterochromatin domains in preserving transcription factor binding through mitosis, and underscore the importance of H3K9me3 for sustaining chromosome architecture and epigenetic memory during cell division.

2023-01-25 | PXD039521 | Pride

Condensin-mediated remodeling of the mitotic chromatin landscape in fission yeast

Project description:Chromatin fibres dynamically change their organisation during cell cycle. In interphase nucleus, chromatin fibres are evenly distributed whereas their spatial occupancy are reorganised to form condensed chromosomes in mitosis. This process called chromosome condensation is necessary for an accomplishment of faithful chromosome segregation. One of the Structural Maintenance of Chromosomes complexes, Condensin, is indispensable for chromosome condensation. It remains, however, unknown how Condensin plays its role in shaping mitotic chromosome. Here we show that chromatin fibres change their interacting partners; short-range contacts in interphase nucleus are converted into long-range interactions to shape condensed chromosomes. This conversion of interactions among chromatin fibres results in the formation of larger domains within mitotic chromosomes. Condensin is solely in charge of the conversion and large domain formation in fission yeast mitosis. Our results show how fission yeast Condensin is involved in shaping mitotic chromosomes.

2017-07-13 | GSE94475 | GEO

Condensin-mediated remodeling of the mitotic chromatin landscape in fission yeast

2017-07-13 | GSE94474 | GEO

Cohesin removal reprograms mitotic gene expression upon mitotic entry [ChIP-seq]

Project description:During mitosis, the genome is restructured to facilitate chromosome segregation, accompanied by dramatic changes in gene expression. However, the mechanisms that underlie mitotic transcriptional regulation are unclear. In contrast to transcribed genes, centromere regions retain transcriptionally active RNA Polymerase II (RNAPII) in mitosis. Here, we demonstrate that chromosome-localized cohesin is necessary and sufficient to retain active RNAPII on mitotic centromeres. Failure to remove cohesin from mitotic chromosome arms dramatically alters mitotic gene expression, and results in a failure to release elongating RNAPII and nascent transcripts from mitotic chromosomes. We propose that prophase cohesin removal is the key step in reprogramming gene expression as cells transition from G2 to mitosis, and is temporally coupled with chromosome condensation to coordinate chromosome segregation with changes in gene expression.

2020-01-30 | GSE139846 | GEO

Cohesin removal reprograms mitotic gene expression upon mitotic entry [RNA-seq II]

2020-01-30 | GSE139845 | GEO

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