Histone acetyltransferase that 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 (PubMed:10026213, PubMed:11545749, PubMed:16543222, PubMed:16543223, PubMed:17189264). Acetylation of histones gives a specific tag for epigenetic transcription activation and elongation (PubMed:10026213, PubMed:11545749, PubMed:16543222, PubMed:16543223, PubMed:17189264, PubMed:19822662). Operates in concert with certain DNA-binding transcriptional activators such as GCN4 or HAP2/3/4 (PubMed:10026213, PubMed:11545749, PubMed:16543222, PubMed:16543223, PubMed:17189264). Its acetyltransferase activity seems to be dependent on the association in different multisubunit complexes (PubMed:10026213, PubMed:11545749, PubMed:16543222, PubMed:16543223, PubMed:17189264). Functions as histone acetyltransferase component of the transcription regulatory histone acetylation (HAT) complexes SAGA, SALSA and ADA (PubMed:10026213, PubMed:12186975, PubMed:9154821). SAGA is involved in RNA polymerase II-dependent transcriptional regulation of approximately 10% of yeast genes (PubMed:10026213). At the promoters, SAGA is required for recruitment of the basal transcription machinery (PubMed:10026213). 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) (PubMed:10026213). SAGA acetylates nucleosomal histone H3 to some extent (to form H3K9ac, H3K14ac, H3K18ac and H3K23ac) (PubMed:10026213). SAGA interacts with DNA via upstream activating sequences (UASs) (PubMed:10026213). SALSA, an altered form of SAGA, may be involved in positive transcriptional regulation (PubMed:12186975). The ADA histone acetyltransferase complex preferentially acetylates nucleosomal histones H3 (to form H3K14ac and H3K18ac) and H2B, leading to transcription regulation (PubMed:9154821). SLIK is proposed to have partly overlapping functions with SAGA (PubMed:12446794, PubMed:15647753). It preferentially acetylates methylated histone H3, at least after activation at the GAL1-10 locus (PubMed:15647753). In addition to histone acetyltransferase, can use different acyl-CoA substrates, such as (2E)-butenoyl-CoA (crotonyl-CoA) and is able to mediate histone crotonylation (PubMed:31699900). acetyl-CoA + L-lysyl-[protein] = CoA + H(+) + N(6)-acetyl-L-lysyl-[protein] (2E)-butenoyl-CoA + L-lysyl-[protein] = CoA + H(+) + N(6)-(2E)-butenoyl-L-lysyl-[protein] Component of the 1.8 MDa SAGA complex, which consists of at least of TRA1, CHD1, SPT7, TAF5, ADA3, SGF73, SPT20/ADA5, SPT8, TAF12, TAF6, HFI1/ADA1, UBP8, GCN5, ADA2, SPT3, SGF29, TAF10, TAF9, SGF11 and SUS1. TAF5, TAF6, TAF9, TAF19, TAF12 and ADA1 seem to be present in 2 copies. SAGA is built of 5 distinct domains with specialized functions. Domain I (containing TRA1) probably represents the activator interaction surface. Domain II (containing TAF5 and TAF6, and probably TAF9 and TAF10), domain III (containing GCN5, TAF10, SPT7, TAF5 and ADA1, and probably ADA2, ADA3 and TAF12), and domain IV (containing HFI1/ADA1 and TAF6, and probably TAF9) are believed to play primarily an architectural role. Domain III also harbors the HAT activity. Domain V (containing SPT3 and SPT20, and probably SPT8) represents the TBP-interacting module, which may be associated transiently with SAGA. SUS1 associates with the SAC3-THP1 complex. Component of the SALSA complex, which consists of at least TRA1, SPT7 (C-terminal truncated form), TAF5, ADA3, SPT20, TAF12, TAF6, HFI1, GCN5, ADA2 and SPT3. Component of the SLIK complex, which consists of at least TRA1, CHD1, SPT7, TAF5, ADA3, SPT20, RTG2, TAF12, TAF6, HFI1, UBP8, GCN5, ADA2, SPT3, SGF29, TAF10 and TAF9. Component of the ADA/GCN5 complex, that consists of HFI1/ADA1, ADA2, ADA3, SPT20/ADA5 and GCN5 and is probably a subcomplex of SAGA. Component of the 0.8 MDa ADA complex, which at least consists of ADA2, ADA3, AHC1 and GCN5. GCN5 interacts with ADA2. Sensitive to amino acid starvation. Present with 1180 molecules/cell in log phase SD medium. Belongs to the acetyltransferase family. GCN5 subfamily.