The function of MBD5 (methyl-CpG binding domain protein 5, Ensembl gene identifier ENSG00000204406) is as follows. Non-catalytic component of the polycomb repressive deubiquitinase (PR-DUB) complex, a complex that specifically mediates deubiquitination of histone H2A monoubiquitinated at 'Lys-120' (H2AK119ub1) (PubMed:24634419). Important for stability of PR-DUB components and stimulating its ubiquitinase activity (PubMed:36180891). As part of the PR-DUB complex, associates with chromatin enriched in histone marks H3K4me1, H3K4me3, and H3K27Ac, but not in H3K27me3 (PubMed:36180891). The PR-DUB complex is an epigenetic regulator of gene expression, including genes involved in cell growth and survivability (PubMed:36180891). MBD5 and MBD6 containing complexes associate with distinct chromatin regions enriched in genes involved in different pathways (PubMed:36180891). Heterochromatin recruitment is not mediated by DNA methylation (PubMed:20700456). The PR-DUB complex is an epigenetic regulator of gene expression, including genes involved in development, cell communication, signaling, cell proliferation and cell viability (PubMed:36180891). {ECO:0000269|PubMed:20700456, ECO:0000269|PubMed:24634419, ECO:0000269|PubMed:36180891}.