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

ABSTRACT: 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.

INSTRUMENT(S): Q Exactive HF-X

ORGANISM(S): Mus Musculus (mouse)

TISSUE(S): Embryonic Stem Cell

SUBMITTER: Holger Kramer

LAB HEAD: Holger Kramer

PROVIDER: PXD030771 | Pride | 2022-10-12

REPOSITORIES: Pride

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Project description:Mitosis entails global alterations to chromosome structure and nuclear architecture, concomitant with transient silencing of transcription. How cells transmit transcriptional states through mitosis remains incompletely understood. While many nuclear factors dissociate from mitotic chromosomes, the observation that certain nuclear factors and chromatin features remain associated with individual loci during mitosis originated the hypothesis that they could provide transcriptional memory through mitosis. To obtain the first genome-wide view of the dynamics of chromatin structure during mitosis, we compared the DNase sensitivity of interphase and mitotic chromatin at two stages of cellular maturation in a rapidly dividingmurine erythroblastmodel. Despite global chromosome condensation visible during mitosis at the microscopic level, the chromatin accessibility landscape is largely unaltered. However, mitotic chromatin accessibility is locally dynamic, with individual loci maintaining none, some, or all of their interphase accessibility. Mitotic reduction in accessibility occurs primarily within narrow, highly hypersensitive sites that frequently coincide with transcription factor binding sites, whereas broader domains of moderate accessibility tend to be more stable. In mitosis, proximal promoters generally maintain their accessibility, whereas distal regulatory elements preferentially lose accessibility. Promoters with the highest degree of accessibility preservation in mitosis tend to also be accessible across many murine tissues in interphase. Transcription factor GATA1 exerts site-specific changes in interphase accessibility that are most pronounced at distal regulatory elements, but does not visibly influence mitotic accessibility. We conclude that features of open chromatin are remarkably stable through mitosis and are modulated at the level of individual genes and regulatory elements. Dnase-Seq data is integrated with Chip-seq [GSE36589, GSE30142] and RNA-seq to examine epigentic changes in mitosis. We performed DNase-seq on two cell lines, G1E and G1E-ER4, both on an asynchronus population, and on a sample of cells in mitosis; each of the 4 experiments in triplicate.

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

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