Component of the transcription regulatory histone acetylation (HAT) complex SAGA, a multiprotein complex that activates transcription by remodeling chromatin and mediating histone acetylation and deubiquitination. Within the SAGA complex, participates in a subcomplex that specifically deubiquitinates both histones H2A and H2B (PubMed:18206972, PubMed:21746879). The SAGA complex is recruited to specific gene promoters by activators such as MYC, where it is required for transcription. Required for nuclear receptor-mediated transactivation. Within the complex, it is required to recruit USP22 and ENY2 into the SAGA complex (PubMed:18206972). Regulates H2B monoubiquitination (H2Bub1) levels. Affects subcellular distribution of ENY2, USP22 and ATXN7L3B (PubMed:27601583). {ECO:0000255|HAMAP- Rule:MF_03047, ECO:0000269|PubMed:18206972, ECO:0000269|PubMed:21746879, ECO:0000269|PubMed:27601583}. This is the function of ATXN7L3 (ataxin 7 like 3, Ensembl gene identifier ENSG00000087152).