function:Component of the Polycomb group (PcG) multiprotein PRC1 complex, a complex required to maintain the transcriptionally repressive state of many genes, including Hox genes, throughout development. 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.,PTM:Phosphorylated upon DNA damage, probably by ATM or ATR.,similarity:Contains 1 FCS-type zinc finger.,similarity:Contains 1 SAM (sterile alpha motif) domain.,subunit:Component of chromatin-associated class II polycomb repressive complex 1 (PRC1/hPRC-H) at least composed of PCGF2/RNF110, BMI1/PCGF4, CBX2/M33, CBX4/PC2, CBX8/PC3, PHC1, PHC2, PHC3, SCMH1, RING1 and RNF2/RING2.,