The dynamic interactome and genomic targets of Polycomb complexes during stem cell differentiation
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ABSTRACT: While the core members of the Polycomb family of proteins (PRC2, PRC1, PR-DUB) are well-characterized, little is known about the specific composition of and protein-protein interactions within these complexes in different cell types. We performed quantitative interaction proteomics and cross-linking mass spectrometry on core Polycomb complex members to identify novel interactors, the relative abundance (stoichiometry) of subunits, and the architecture of these complexes in mouse embryonic stem cells (mESCs) and neural progenitor cells (NPCs). Differentiation to NPCs resulted in dramatic binding changes for several substoichiometric interactors of PRC2 and PRC1. ChIP-seq of core PRC2 and PRC1 subunits in mESCs and NPCs also identified dynamic changes in the genomic localization of these complexes. We observed a loss of PRC2 from most H3K27me3 sites during differentiation, whereas PRC1 is retained at these sites. Additionally, we found PRC1 at enhancers and promoters of active genes independent of PRC2 binding. Overexpression studies using NPC-specific PRC1 interactors demonstrated that the subunit switching observed during differentiation can change PRC1 target site binding. Altogether, these findings extend our understanding of Polycomb family composition, architecture, and genome-wide localization. ChIP-seq samples for Suz12, Ezh2, Ring1b, Pcgf2, and inputs from mouse embryonic stems cells (mES) and neural progenitor cells (NPC) as well as NPC histone H3K4me1 ChIP-seq.
Project description:While the core members of the Polycomb family of proteins (PRC2, PRC1, PR-DUB) are well-characterized, little is known about the specific composition of and protein-protein interactions within these complexes in different cell types. We performed quantitative interaction proteomics and cross-linking mass spectrometry on core Polycomb complex members to identify novel interactors, the relative abundance (stoichiometry) of subunits, and the architecture of these complexes in mouse embryonic stem cells (mESCs) and neural progenitor cells (NPCs). Differentiation to NPCs resulted in dramatic binding changes for several substoichiometric interactors of PRC2 and PRC1. ChIP-seq of core PRC2 and PRC1 subunits in mESCs and NPCs also identified dynamic changes in the genomic localization of these complexes. We observed a loss of PRC2 from most H3K27me3 sites during differentiation, whereas PRC1 is retained at these sites. Additionally, we found PRC1 at enhancers and promoters of active genes independent of PRC2 binding. Overexpression studies using NPC-specific PRC1 interactors demonstrated that the subunit switching observed during differentiation can change PRC1 target site binding. Altogether, these findings extend our understanding of Polycomb family composition, architecture, and genome-wide localization.
Project description:While the core subunits of Polycomb group (PcG) complexes are well characterized, little is known about the dynamics of these protein complexes during cellular differentiation. We used quantitative interaction proteomics to study PcG proteins in mouse embryonic stem cells (mESCs) and neural progenitor cells (NPCs). We found the stoichiometry of PRC1 and PRC2 to be highly dynamic during neural differentiation.
Project description:Polycomb Repressive Complexes PRC1 and PRC2 play a crucial role in silencing lineage-specific genes during early embryogenesis. To provide new insights in polycomb biology, we profiled the proximal interactome (proxeome) of the catalytic subunits RNF2 (PRC1) and EZH2 (PRC2) in mouse embryonic stem cells (mESCs). This revealed >100 proteins proximal to PRC2 and PRC1, which mainly comprise transcription factors, transcriptional regulators and RNA binding proteins. Interestingly, the EZH2 proxeome included both PRC complexes, while the RNF2 proxeome only identified PRC1 subunits. More than half of the PRC2 proximal proteins are shared with PRC1, revealing the molecular constitution of polycomb chromatin domains. We identified several pluripotency-associated transcription factors, including NANOG, for which we confirmed genomic co-localisation with PRC2. Upon PRC2 disruption, NANOG redistributes to specific sites containing its DNA binding motif. Finally, we compared PRC2 proximal interactomes between naïve mESCs, serum-cultured mESCs and embryoid bodies, altogether providing a comprehensive resource in different cellular contexts that may help to further decipher Polycomb biology.
Project description:Polycomb Repressive Complexes PRC1 and PRC2 play a crucial role in silencing lineage-specific genes during early embryogenesis. To provide new insights in polycomb biology, we profiled the proximal interactome (proxeome) of the catalytic subunits RNF2 (PRC1) and EZH2 (PRC2) in mouse embryonic stem cells (mESCs). This revealed >100 proteins proximal to PRC2 and PRC1, which mainly comprise transcription factors, transcriptional regulators and RNA binding proteins. Interestingly, the EZH2 proxeome included both PRC complexes, while the RNF2 proxeome only identified PRC1 subunits. More than half of the PRC2 proximal proteins are shared with PRC1, revealing the molecular constitution of polycomb chromatin domains. We identified several pluripotency-associated transcription factors, including NANOG, for which we confirmed genomic co-localisation with PRC2. Upon PRC2 disruption, NANOG redistributes to specific sites containing its DNA binding motif. Finally, we compared PRC2 proximal interactomes between naïve mESCs, serum-cultured mESCs and embryoid bodies, altogether providing a comprehensive resource in different cellular contexts that may help to further decipher Polycomb biology.
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.
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.
Project description:Polycomb Repressive Complexes PRC1 and PRC2 play a crucial role in silencing lineage-specific genes during early embryogenesis. To provide new insights in polycomb biology, we profiled the proximal interactome (proxeome) of the catalytic subunits RNF2 (PRC1) and EZH2 (PRC2) in mouse embryonic stem cells (mESCs). This revealed >100 proteins proximal to PRC2 and PRC1, which mainly comprise transcription factors, transcriptional regulators and RNA binding proteins. Interestingly, the EZH2 proxeome included both PRC complexes, while the RNF2 proxeome only identified PRC1 subunits. More than half of the PRC2 proximal proteins are shared with PRC1, revealing the molecular constitution of polycomb chromatin domains. We identified several pluripotency-associated transcription factors, including NANOG, for which we confirmed genomic co-localisation with PRC2. Upon PRC2 disruption, NANOG redistributes to specific sites containing its DNA binding motif. Finally, we compared PRC2 proximal interactomes between naïve mESCs, serum-cultured mESCs and embryoid bodies, altogether providing a comprehensive resource in different cellular contexts that may help to further decipher Polycomb biology.
Project description:Polycomb Repressive Complexes PRC1 and PRC2 play a crucial role in silencing lineage-specific genes during early embryogenesis. To provide new insights in polycomb biology, we profiled the proximal interactome (proxeome) of the catalytic subunits RNF2 (PRC1) and EZH2 (PRC2) in mouse embryonic stem cells (mESCs). This revealed >100 proteins proximal to PRC12 and PRC21, which mainly comprise transcription factors, transcriptional regulators and RNA binding proteins. To investigate the link between PRC2 and NuA4, and therefore the the link between H4ac an H3K27me3, we perturbed PRC2 both chemically and genetically.The effects on the histone PTMs were measured with LC-MS/MS.
Project description:The chromatin modifying activities inherent to polycomb repressive complexes PRC1 and PRC2 play an essential role in gene regulation, cellular differentiation, and development. However, the mechanisms by which these complexes recognize their target sites and function together to form repressive chromatin domains remain poorly understood. Recruitment of PRC1 to target sites has been proposed to occur through a hierarchical process, dependent on the prior nucleation of PRC2 and placement of H3K27me3. Here, using a de novo targeting assay in mouse embryonic stem cells we unexpectedly discover that PRC1-dependent H2AK119ub1 leads to the recruitment of PRC2 and H3K27me3 to effectively initiate a polycomb domain. Genetic ablation of catalytic subunit of the PRC1 complex (RINGA/B) and ChIP-seq analysis of PRC1 and PRC2 components confirmed genome-wide decreases in PRC2 occupancy and H3K27me3 levels at PRC target sites. This activity is restricted to variant PRC1 complexes and genetic ablation experiments reveal that targeting of the variant PCGF1/PRC1 complex by KDM2B to CpG islands is required for polycomb domain formation and normal development. Together these observations provide a surprising new PRC1-dependent logic for PRC2 occupancy and polycomb domain formation. RING1A-/-;RING1Bfl/fl ES cells were treated with 800M-BM-5M tamoxifen for 48hours and compared to untreated control cells by ChIP-seq for RING1B, SUZ12, EZH2 and H3K27me3.
Project description:The established hierarchical model explaining co-occupancy of Polycomb repressor complexes 1 and 2 (PRC 1 and 2) at target loci proposes that the chromodomain of the polycomb protein, a core PRC1 subunit, recognises the H3K27me3 histone modification catalysed by PRC2. We used chromatin immunoprecipitation to analyse PRC1 occupancy at target loci in Eed-/- mouse embryonic stem cells (ESCs) that lack H3K27me3. Occupancy of the core PRC1 proteins Ring1B and Mel18 was strongly reduced, consistent with the hierarchical model. However, levels of H2A ubiquitylation (H2AK119u1), the histone modification catalysed by PRC1, were similar to wild-type cells, suggesting PRC1 recruitment is independent of H3K27me3. ChIP-sequencing analysis of Ring1B occupancy genome wide substantiated this conclusion, demonstrating significant Ring1B levels at polycomb target loci in Eed-/- ESCs. Thus PRC1 and PRC2 are recruited independently to sites that they co-occupy. We conclude that the primary function of H3K27me3 is to increase the residency of PRC1 at target loci and thereby to contribute to the stability of PRC1 mediated silencing. Examination of Ring1B binding in WT, Eed ko and Input of ESCs Examination of CBX7 in WT and Eed ko of ESCs