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. 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 (PubMed:18206972, PubMed:27601583). Interacts directly with ATXN7L3; leading to its recruitment to the SAGA complex (PubMed:18206972). Interacts with ATXN7L3 and weakly with ATXN7L3B (PubMed:27601583). Moderately expressed in various tissues including heart and skeletal muscle, and weakly expressed in lung and liver. Belongs to the peptidase C19 family. UBP8 subfamily.