E3 ubiquitin-protein ligase required to prevent centriole reduplication (PubMed:15885686, PubMed:23769972). Probably acts by ubiquitinating positive regulators of centriole reduplication (PubMed:23769972). Mediates monoubiquitination of 'Lys-119' of histone H2A (H2AK119Ub), a specific tag for epigenetic transcriptional repression: associates with some Polycomb group (PcG) multiprotein PRC2-like complex and mediates repression of target genes (PubMed:25470042). Has anti-HIV activity (PubMed:24317724). S-ubiquitinyl-[E2 ubiquitin-conjugating enzyme]-L-cysteine + [acceptor protein]-L-lysine = [E2 ubiquitin-conjugating enzyme]-L-cysteine + N(6)-ubiquitinyl-[acceptor protein]-L-lysine. Protein modification; protein ubiquitination. Associates with the PRC2/EED-EZH2 complex. Found in vesicles of the peroxisome. Aggregates as aggresomes, a perinuclear region where certain misfolded or aggregated proteins are sequestered for proteasomal degradation. Ubiquitous (PubMed:10888877). Highly expressed in testis, while it is weakly expressed in other tissues (PubMed:16310976). Overexpressed in a number of breast cancer cell lines. Auto-ubiquitinated. The disease is caused by variants affecting the gene represented in this entry. Acts as a proto-oncogene via its ability to monoubiquinate 'Lys-119' of histone H2A (H2AK119Ub): overexpressed in a number of breast cancers and promotes transformation of cells by mediating silencing of tumor suppressor genes (PubMed:25470042). Belongs to the TRIM/RBCC family.