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Trichostatin A Treatment Has Little Impact on Nuclear compartments in Cells Depleted of H3K9me, H3K27me3, and uH2A [ChIP-Seq]

ABSTRACT: In the mammalian nucleus, heterochromatin is segregated from transcriptionally active euchromatic regions (A compartments), forming large, condensed, and inactive nuclear compartments (B compartments). However, the mechanisms underlying its spatial organization remain incompletely understood. We previously demonstrated that simultaneous depletion of H3K9 methylation, H3K27me3, and H2A monoubiquitination in immortalized mouse embryonic fibroblasts (iMEFs) leads to heterochromatin weakening and alterations in nuclear compartments. However, the overall pattern of A/B compartments remains largely preserved even under these conditions, suggesting the involvement of unknown factors. Since histone deacetylation is a key factor in transcriptional repression, we investigated the impact of histone deacetylase (HDAC) inhibition on nuclear compartments by treating cells depleted of H3K9 methylation, H3K27me3, and H2A K119 monoubiquitylation (H2AK119ub/uH2A) with the HDAC inhibitor Trichostatin A (TSA). We performed Hi-C analysis to assess the nuclear compartment changes. Our results showed that, although TSA treatment globally increased H3K27ac levels, the difference in H3K27ac enrichment between A/B compartments remained evident, and nuclear compartments were minimally affected. These findings suggest that factors other than HDACs maintain nuclear compartmentalization when repressive chromatin modifications are depleted.

ORGANISM(S): Mus musculus

PROVIDER: GSE294421 | GEO | 2025/04/30

REPOSITORIES: GEO

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Project description:Polycomb group (PcG) proteins control organism development by regulating the expression of developmental genes. Transcriptional regulation by PcG proteins is achieved at least partly through the PRC2-mediated methylation on lysine 27 of histone H3 (H3K27) and PRC1-mediated ubiquitylation on lysine 119 of histone H2A (uH2A). As an integral component of PRC1, Bmi1 has been demonstrated to be critical for H2A ubiquitylation. Although recent studies have revealed the genome wide binding patterns of some of the PRC1 and PRC2 components, as well as the H3K27me3 mark, there have been no reports describing genome wide localization of uH2A. Using the recently developed ChIP-Seq technology, here we report genome wide localization of the Bmi1-dependent uH2A mark in MEF cells. Gene promoter averaging analysis indicates a peak of uH2A just inside the transcription start site (TSS) of well annotated genes. This peak is enriched at promoters containing the H3K27me3 mark and represents the least expressed genes in WT MEF cells. In addition, peak finding reveals regions of local uH2A enrichment throughout the mouse genome, including almost 700 gene promoters. Genes with promoter peaks of uH2A exhibit lower level expression when compared to genes that do not contain promoter peaks of uH2A. Moreover, we demonstrate that genes with uH2A peaks have increased expression upon Bmi1 knockout. Importantly, local enrichment of uH2A is not limited to regions containing the H3K27me3 mark. We provide evidence to suggest that DNA methylation is tightly linked to H2A ubiquitylation in high density CpG promoters. Thus, our work not only reveals Bmi1-dependent H2A ubiquitylation but also suggests that uH2A targeting in differentiated cells may employ a different mechanism from that in ES cells. Experiment Overall Design: RNA was extracted from wild-type MEF cells which were immortalized through TBX2 overexpression, amplified, labeled, and hybridized to an Affymetrix 430 2 microarray. In parallel, RNA was prepared from TBX2-immortalized Bmi1 null MEF cells and hybridized to an Affymetrix 430 2 microarray.

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Trichostatin A Treatment Has Little Impact on Nuclear compartments in Cells Depleted of H3K9me, H3K27me3, and uH2A [ChIP-Seq]

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