Component of a Polycomb group (PcG) multiprotein PRC1-like complex, a complex class required to maintain the transcriptionally repressive state of many genes, including Hox genes, throughout development (By similarity). PcG PRC1 complex acts via chromatin remodeling and modification of histones; it mediates monoubiquitination of histone H2A 'Lys-119', rendering chromatin heritably changed in its expressibility (By similarity). Binds to histone H3 trimethylated at 'Lys-9' (H3K9me3) or at 'Lys-27' (H3K27me3) (PubMed:16537902). Plays a role in the lineage differentiation of the germ layers in embryonic development (PubMed:22226355). Involved in sexual development, acting as activator of NR5A1 expression (By similarity). Component of a PRC1-like complex (By similarity). The composition of the PRC1 complex may differ between the PRC1 complex in pluripotent embryonic stem cells containing RNF2, CBX7 and PCGF2, and the PRC1 complex in differentiating cells containing RNF2, CBX2, CBX4 and BMI1 (PubMed:22226355). Interacts with RING1/RNF2 (PubMed:9312051, PubMed:22226355). Interacts (via chromodomain) with histone H3K9Me3 and H3K27me3 (PubMed:16537902). May interact with H3C15 and H3C1 (By similarity). Localizes to the inactivated X chromosome in females. Expressed in embryoid bodies. Expressed in most embryonic tissues except the heart from 8.5 to 11.5 dpc. Expressed in central nervous system (CNS, ventricular zone and spinal cord), peripheral nervous system (PNS, sensory cranial and spinal ganglia), olfactory and tongue epithelia, lung, gastrointestinal duct and urogenital system at 13.5 dpc. Expressed in CNS, thymus, various epithelial cell types including the olfactory, tooth and tongue epithelia at 15.5 dpc.