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. 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. Required for proper control of cellular levels of GMNN expression. {ECO:0000269|PubMed:23418308}.