Synonyms:Deubiquitinating enzyme 21, Ubiquitin thiolesterase 21, USP16, USP21, USP23 Background:Deubiquitinates histone H2A, a specific tag for epigenetic transcriptional repression, thereby acting as a coactivator. Deubiquitination of histone H2A releaves the repression of di-and trimethylation of histone H3 at 'Lys-4', resulting in regulation of transcriptional initiation. Regulates gene expression via histone H2A deubiquitination(By similarity). Also capable of removing NEDD8 from NEDD8 conjugates but has no effect on Sentrin-1 conjugates(PubMed:10799498). Deubiquitinates BAZ2A/TIP5 leading to its stabilization(PubMed:26100909).