Histone deubiquitinating component of the transcription regulatory histone acetylation (HAT) complex SAGA. Catalyzes the deubiquitination of both histones H2A and H2B, thereby acting as a coactivator. Recruited to specific gene promoters by activators such as MYC, where it is required for transcription. Required for nuclear receptor-mediated transactivation and cell cycle progression (By similarity). Thiol-dependent hydrolysis of ester, thioester, amide, peptide and isopeptide bonds formed by the C-terminal Gly of ubiquitin (a 76-residue protein attached to proteins as an intracellular targeting signal). Component of some SAGA transcription coactivator-HAT complexes, at least composed of ATXN7, ATXN7L3, ENY2, GCN5L2, SUPT3H, TAF10, TRRAP and USP22. Within the SAGA complex, ATXN7L3, ENY2 and USP22 form a subcomplex required for histone deubiquitination. Interacts directly with ATXN7L3; leading to its recruitment to the SAGA complex. Interacts with ATXN7L3 and weakly with ATXN7L3B. Highly expressed in brain and weakly in other organs. Highly expressed between 10.5 dpc and 12.5 dpc. Expressed in the midbrain, forebrain, hindbrain and dorsal root ganglia of embryos at 12.5 dpc. Belongs to the peptidase C19 family. UBP8 subfamily.