Variant PRC1 complex-dependent H2A ubiquitylation drives PRC2 recruitment and polycomb domain formation.
Bottom Line: Chromatin modifying activities inherent to polycomb repressive complexes PRC1 and PRC2 play an essential role in gene regulation, cellular differentiation, and development.Here, using a de novo targeting assay in mouse embryonic stem cells we unexpectedly discover that PRC1-dependent H2AK119ub1 leads to recruitment of PRC2 and H3K27me3 to effectively initiate a polycomb domain.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 normal polycomb domain formation and mouse development.
Affiliation: Laboratory of Chromatin Biology and Transcription, Department of Biochemistry, University of Oxford, Oxford, OX1 3QU, UK.Show MeSH
Mentions: The unexpected observation that variant PRC1 complexes can nucleate PRC2 to establish a polycomb domain de novo suggests that a feature associated with variant complex occupancy, perhaps H2AK119ub1, is responsible for this activity (Figure 1). To test this possibility, a single polypeptide fusion between the dimerization domains of RING1B and PCGF4 was engineered and fused to TetR (Bentley et al., 2011; Buchwald et al., 2006; Li et al., 2006). This minimal RING1B/PCGF4 catalytic domain (RPCD) does not form normal PRC1 complexes (Figure 3A) but retains H2AK119ub1 E3 ligase activity (Figure 3B) (Cooper et al., 2014) leading to a striking enrichment of EZH2, SUZ12, and H3K27me3 at the TetO (Figure 3B). When mutations were engineered in TetR-RPCD (TetR-RPCDmut), rendering it incapable of catalyzing H2AK119ub1, PRC2 and H3K27me3 were no longer recruited to the TetO (Figure 3B). This suggests that H2AK119ub1, and not simply binding of PRC1 complexes, is the central determinant driving PRC1-dependent recruitment of PRC2.
Affiliation: Laboratory of Chromatin Biology and Transcription, Department of Biochemistry, University of Oxford, Oxford, OX1 3QU, UK.