Functional dissection of PRC1 subunits RYBP and YAF2 during neural differentiation of embryonic stem cells

Polycomb repressive complex 1 (PRC1) comprises two different complexes: CBX-containing canonical PRC1 (cPRC1) and RYBP/YAF2-containing variant PRC1 (vPRC1). RYBP and its paralog YAF2 recruit vPRC1 to catalyze H2AK119ub through a positive-feedback model. Here, we show that expression of RYBP and YAF2 decreases and increases, respectively, during neural differentiation of embryonic stem cells (ESCs). Rybp knockout impairs neural differentiation by activating Wnt signaling and derepressing nonneuroectoderm-associated genes. However, Yaf2 knockout promotes neural differentiation and leads to redistribution of RYBP binding, increases enrichment of RYBP and H2AK119ub on the RYBP-YAF2 co-targeted genes, and prevents ectopic derepression of nonneuroectoderm-associated genes in neural-differentiated cells. Furthermore, the phase separations mediated by RYBP alone or together with RING1B are easier and more stable than those by YAF2, which might facilitate the deposition of H2AK119ub more abundantly by RYBP-PRC1 than YAF2-PRC1. Together, this study reveals that RYBP might maintain repressed chromatin more strongly and function differentially in regulating mESC neural differentiation compared with YAF2. Overall design: Comparative gene expression profiling analysis of RNA-seq data in wild-type, Rybp-/- and Yaf2-/- mESCs and their neural differentiated cells.