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MSWI/SNF promotes polycomb repression both directly and through genome-wide redistribution [ChIP-seq]

ABSTRACT: The mammalian SWI/SNF, or BAF complex, has a conserved and direct role in antagonizing polycomb-mediated repression. Yet, BAF also promotes repression by polycomb in stem cells and cancer. How BAF both antagonizes and promotes polycomb-mediated repression remains unknown. Here, we utilize targeted protein degradation to dissect the BAF-polycomb axis in embryonic stem cells on short timescales. We report that rapid BAF depletion redistributes PRC1 and PRC2 complexes from highly occupied domains, like Hox clusters, to weakly occupied sites normally opposed by BAF. Polycomb redistribution from highly repressed domains results in their decompaction, gain of active epigenomic features, and transcriptional derepression. Surprisingly, through dose-dependent degradation of PRC1 & PRC2 we identify a conventional role for BAF in polycomb-mediated repression, in addition to global polycomb redistribution. These findings provide new mechanistic insight into the highly dynamic state of the Polycomb-Trithorax axis.

ORGANISM(S): Mus musculus

PROVIDER: GSE173550 | GEO | 2021/06/11

REPOSITORIES: GEO

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mSWI/SNF promotes polycomb repression both directly and through genome-wide redistribution [RNA-seq]

Project description:The mammalian SWI/SNF, or BAF complex, has a conserved and direct role in antagonizing polycomb-mediated repression. Yet, BAF also promotes repression by polycomb in stem cells and cancer. How BAF both antagonizes and promotes polycomb-mediated repression remains unknown. Here, we utilize targeted protein degradation to dissect the BAF-polycomb axis in embryonic stem cells on short timescales. We report that rapid BAF depletion redistributes PRC1 and PRC2 complexes from highly occupied domains, like Hox clusters, to weakly occupied sites normally opposed by BAF. Polycomb redistribution from highly repressed domains results in their decompaction, gain of active epigenomic features, and transcriptional derepression. Surprisingly, through dose-dependent degradation of PRC1 & PRC2 we identify a conventional role for BAF in polycomb-mediated repression, in addition to global polycomb redistribution. These findings provide new mechanistic insight into the highly dynamic state of the Polycomb-Trithorax axis.

2021-06-11 | GSE173499 | GEO

Two distinct functional axes of positive feedback-enforced PRC2 recruitment in mouse embryonic stem cells

Project description:Polycomb Repressive Complex 2 (PRC2) plays an essential role in development by catalysing trimethylation of histone H3 lysine 27 (H3K27me3), resulting in gene repression. PRC2 consists of two sub-complexes, PRC2.1 and PRC2.2, in which the PRC2 core associates with distinct ancillary subunits such as MTF2 and JARID2, respectively. Both MTF2, present in PRC2.1, and JARID2, present in PRC2.2, play a role in core PRC2 recruitment to target genes in mouse embryonic stem cells (mESCs). However, it remains unclear how these distinct sub-complexes cooperate to establish H3K27me3 domains. Here, we combine a range of Polycomb mutant mESCs with chemical inhibition of PRC2 catalytic activity, to systematically dissect their relative contributions to PRC2 binding to target loci. We find that PRC2.1 and PRC2.2 mediate two distinct paths for recruitment, with mutually reinforced binding. Part of the cross-talk between PRC2.1 and PRC2.2 occurs via their catalytic product H3K27me3, which is bound by the PRC2 core-subunit EED, thereby mediating a positive feedback. Strikingly, removal of either JARID2 or H3K27me3 only has a minor effect on PRC2 recruitment, whereas their combined ablation largely attenuates PRC2 recruitment. This strongly suggests an unexpected redundancy between JARID2 and EED-H3K27me3-mediated recruitment of PRC2. Furthermore, we demonstrate that all core PRC2 recruitment occurs through the combined action of MTF2-mediated recruitment of PRC2.1 to DNA and PRC1-mediated recruitment of JARID2-containing PRC2.2. Both axes of binding are supported by EED-H3K27me3 positive feedback, but to a different degree. Finally, we provide evidence that PRC1 and PRC2 mutually reinforce reciprocal binding. Together, these data disentangle the interdependent and cooperative interactions between Polycomb complexes that are important to establish Polycomb repression at target sites.

2021-09-22 | PXD020684 | Pride

Two distinct functional axes of positive feedback-enforced PRC2 recruitment in mouse embryonic stem cells

2020-08-07 | PXD014290 | Pride

R-loops and PRC1 repress Polycomb-target genes in mouse embryonic stem cells

Project description:R-loops are three-stranded nucleic acid structures that form naturally during transcription, especially over unmethylated CpG-rich promoters. In mESC, such promoters of developmental regulator genes are occupied by the Polycomb-repressor complexes PRC1 and PRC2. Here we have explored the possibility that R-loops form over Polycomb-repressed genes and play a role in their transcriptional silencing. Using single gene and genome-wide analyses, we show that R-loops form at a specific subset of PRC-target genes and contribute to Polycomb occupancy on chromatin. Removal of R-loops leads to an up-regulation of nascent and processed transcripts and the appearance of the elongating form of RNA polymerase II. In contrast, removal of PRC2 does not influence R-loop formation, transcriptional repression and PRC1 recruitment. We finally show that R-loops and PRC1 can repress Polycomb-target genes in the absence of PRC2. Our results uncover an unanticipated synergy between R-loops and PRC1 in Polycomb repression mechanisms.

2019-03-19 | GSE118115 | GEO

Chromatin immunoprecipitation of mouse polycomb group (PcG) proteins in embryonic stem cells

Project description:Polycomb group (PcG) proteins are highly conserved from flies to mammals and many of these factors have essential roles in early embryonic development. PcG proteins comprise two multimeric complexes, the Polycomb Repressive complexes 1 and 2 (PRC1 and 2), which have been shown to repress transcription through epigenetic modification of chromatin structure. To gain insight into the role of Polycomb in early development, we have identified PRC1 and PRC2 target genes in mouse embryonic stem (ES) cells using genome-scale location analysis. We found that PRC2 occupies many genes that encode key regulators of development including those encoding transcription factors and components of signaling pathways. These genes are repressed and contain nucleosomes methylated at lysine 27 on histone H3. The majority of PRC2 bound and methylated target genes are co-occupied by PRC1 indicating that these complexes function at a similar set of genes in ES cells. Lack of PRC1 or PRC2 subunits in ES cells results in derepression of target genes and loss of pluripotency. These results provide insight into how PcG proteins contribute to the maintenance of stem cell identity.

2006-05-09 | E-WMIT-12 | biostudies-arrayexpress

PRC1 drives Polycomb-mediated gene repression by controlling transcription initiation and burst frequency [RNA-seq]

Project description:The Polycomb repressive system plays a fundamental role in controlling gene expression during mammalian development. To achieve this, Polycomb repressive complexes 1 and 2 (PRC1 and PRC2) bind target genes and use histone modification-dependent feedback mechanisms to form Polycomb chromatin domains and repress transcription. The interrelatedness of PRC1 and PRC2 activity at these sites has made it difficult to discover the specific components of Polycomb chromatin domains that drive gene repression and to understand mechanistically how this is achieved. Here, by exploiting rapid degron-based approaches and time-resolved genomics we kinetically dissect Polycomb-mediated repression and discover that PRC1 functions independently of PRC2 to counteract RNA polymerase II binding and transcription initiation. Using single-cell gene expression analysis, we reveal that PRC1 acts uniformly within the cell population, and that repression is achieved by controlling transcriptional burst frequency. These important new discoveries provide a mechanistic and conceptual framework for Polycomb-dependent transcriptional control.

2021-07-21 | GSE159399 | GEO

PRC1 drives Polycomb-mediated gene repression by controlling transcription initiation and burst frequency [ChIP-seq]

2021-07-21 | GSE159398 | GEO

Expression data from wild type, Ring1B-/-, Eed-/-, and Ring1B/Eed double deficient mouse ES cells

Project description:Polycomb complexes establish chromatin modifications for maintaining gene repression and are essential for embryonic development in mice. Here we use pluripotent embryonic stem (ES) cells to demonstrate an unexpected redundancy between Polycomb repressive complex 1 (PRC1) and PRC2 during the formation of differentiated cells. ES cells lacking the function of either PRC1 or PRC2 can differentiate into cells of the three germ layers, whereas simultaneous loss of PRC1 and PRC2 abrogates differentiation. On the molecular level the differentiation defect is caused by the derepression of a set of genes that is redundantly repressed by PRC1 and PRC2 in ES cells. Furthermore, we find that genomic repeats are Polycomb targets and show that in the absence of Polycomb complexes endogenous MLV elements can mobilize. This indicates a contribution of the PcG system to the defense against parasitic DNA and a potential role of genomic repeats in Polycomb mediated gene regulation. RNA from wt and PcG mutant ES cells was extracted using Trizol and hybridized to an Affymetrix Mouse 430_2.0 chip. Labeling, hybridization and primary data analysis were performed by a commercial provider (Atlas Biolabs, Berlin). Before RNA extraction, the undifferentiated ES cell state was confirmed by colony morphology. All genotypes were hybridized in biological triplicates.

2009-11-30 | E-GEOD-19076 | biostudies-arrayexpress

Expression data from wild type, Ring1B-/-, Eed-/-, and Ring1B/Eed double deficient mouse ES cells

2009-12-01 | GSE19076 | GEO

VAL1 acts as an assembly platform co-ordinating co-transcriptional repression and chromatin 2 regulation at Arabidopsis FLC

Project description:• Polycomb (PcG) regulation is crucial for development across eukaryotes, but how PcG targets are specified is still incompletely understood. The slow timescale of cold-induced Polycomb Repressive Complex 2 silencing during vernalization at Arabidopsis thaliana FLOWERING LOCUS C (FLC) provides an excellent system to elucidate the sequence of events. Association of the DNA binding protein VAL1 to an FLC intronic RY motif within the PcG nucleation region is an important step. VAL1 is associated in vivo with APOPTOSIS AND SPLICING ASSOCIATED PROTEIN (ASAP) complex and Polycomb Repressive Complex 1 (PRC1). Here, we show that ASAP and PRC1 functions are necessary for co-transcriptional repression and chromatin regulation during FLC silencing. ASAP mutants affect FLC transcription in warm conditions, but the rate of FLC silencing in the cold is unaffected. PRC1-mediated H2Aub accumulation increases at the nucleation region upon exposure to cold, but unlike the PRC2-delivered H3K27me3 does not spread across the locus. H2Aub is thus involved in the transition to epigenetic silencing at FLC facilitating H3K27me3 accumulation, which in turn is necessary for long-term epigenetic memory. Overall, our work highlights the importance of the DNA sequence-specific binding protein VAL1 as an assembly platform coordinating the co-transcriptional repression and chromatin regulation necessary for the epigenetic silencing of FLC.

2022-10-13 | PXD036548 | Pride

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