Acetylates histone H2B to form H2BK11ac and H2BK16ac; histone H3 to form H3K9ac; H3K14ac; H3K18ac; H3K23ac; H3K27ac and H3K36ac; with a lower preference histone H4 to form H4K8ac and H4K16ac; and contributes to H2A.Z acetylation. Acetylation of histones gives a specific tag for epigenetic transcription activation. Operates in concert with certain DNA-binding transcriptional activators such as GCN4 or HAP2/3/4. Its acetyltransferase activity seems to be dependent on the association in different multisubunit complexes. Functions as histone acetyltransferase component of the transcription regulatory histone acetylation (HAT) complexes SAGA; SALSA and ADA. SAGA is involved in RNA polymerase II-dependent transcriptional regulation of approximately 10% of yeast genes. At the promoters; SAGA is required for recruitment of the basal transcription machinery. It influences RNA polymerase II transcriptional activity through different activities such as TBP interaction (SPT3; SPT8 and SPT20) and promoter selectivity; interaction with transcription activators (GCN5; ADA2; ADA3 and TRA1); and chromatin modification through histone acetylation (GCN5) and deubiquitination (UBP8). SAGA acetylates nucleosomal histone H3 to some extent (to form H3K9ac; H3K14ac; H3K18ac and H3K23ac). SAGA interacts with DNA via upstream activating sequences (UASs). SALSA; an altered form of SAGA; may be involved in positive transcriptional regulation. The ADA histone acetyltransferase complex preferentially acetylates nucleosomal histones H3 (to form H3K14ac and H3K18ac) and H2B; leading to transcription regulation. SLIK is proposed to have partly overlapping functions with SAGA. It preferentially acetylates methylated histone H3; at least after activation at the GAL1-10 locus. {ECO:0000269|PubMed:10026213; ECO:0000269|PubMed:16543222; ECO:0000269|PubMed:16543223}.