InterPro domain: IPR037796

The transcription regulatory histone acetylation complex Spt-Ada-Gcn5 acetyltransferase (SAGA) is involved in RNA polymerase II-dependent transcriptional regulation of approximately 10% of yeast genes. SAGA preferentially acetylates histones H3 and H2B and deubiquitinates histone H2B [ 1 ]. SAGA is known as PCAF in vertebrates and PCAF acetylates nucleosomal histone H3 [ 2 ]. The SAGA complex consists of at least TRA1, CHD1, SPT7, TAF5, ADA3, SGF73, SPT20/ADA5, SPT8, TAF12, TAF6, HFI1/ADA1, UBP8, GCN5, ADA2, SPT3, SGF29, TAF10, TAF9, SGF11 and SUS1, and some of these components are present as two copies. The complex is built up from distinct modules, each of which has a separate function and crosslinks with either other proteins or other modules in the complex [ 3 ].

SLIK (SAGA-like) is a multi-subunit histone acetyltransferase complex that preferentially acetylates histones H3 and H2B and deubiquitinates histone H2B. It is an embellishment of the SAGA complex. The yeast SLIK complex consists of at least TRA1, CHD1, SPT7, CC TAF5, ADA3, SPT20, RTG2, TAF12, TAF6, HFI1, UBP8 (a deubiquitinase), GCN5, ADA2, SPT3, SGF29, TAF10 and TAF9 [ 4 , 4 ].

The yeast SALSA complex is an altered form of the SAGA complex and consists of at least TRA1, SPT7 (C-terminal truncated form), TAF5, ADA3, SPT20, TAF12, TAF6, HFI1, GCN5, ADA2 and SPT3 [ 5 ].

The DNA-binding general transcription factor complex TFIID is central to the initiation of DNA-dependent RNA polymerase II transcription. TFIID is the only general transcription initiation factor that bind to the TATA box. The binding of TFIID to the TATA-box is the first step in the formation of a complex able to initiate transcription [ 6 ]. TFIID consists of the TATA binding protein (TBP) and 14 TBP-associated factors (TAFs). One copy of each TAF1, TAF2, TAF3, TAF7, TAF8, TAF11, TAF13, two copies of each TAF4, TAF5, TAF6, TAF9, TAF10, TAF12, and three copies of TAF14 [ 7 ].

Transcription initiation factor TFIID subunit 6 (TAF6) is a component of the DNA-binding general transcription factor complex TFIID [ 8 ] and the regulatory transcription regulatory histone acetylation (HAT) complexes SAGA [ 8 ], SALSA [ 9 ] and SLIK [ 9 ].

1. Chd1 chromodomain links histone H3 methylation with SAGA- and SLIK-dependent acetylation. Nature 433, 434-8
2. Histone-like TAFs within the PCAF histone acetylase complex. Cell 94, 35-44
3. Architecture of the Saccharomyces cerevisiae SAGA transcription coactivator complex. EMBO J. 33, 2534-46
4. The novel SLIK histone acetyltransferase complex functions in the yeast retrograde response pathway. Mol. Cell. Biol. 22, 8774-86
5. SALSA, a variant of yeast SAGA, contains truncated Spt7, which correlates with activated transcription. Proc. Natl. Acad. Sci. U.S.A. 99, 11622-7
6. The general transcription factors of RNA polymerase II. Genes Dev. 10, 2657-83
7. Identification of two novel TAF subunits of the yeast Saccharomyces cerevisiae TFIID complex. J. Biol. Chem. 275, 13895-900
8. A subset of TAF(II)s are integral components of the SAGA complex required for nucleosome acetylation and transcriptional stimulation. Cell 94, 45-53