TBP-associated factor
Protein domains
From Wikipedia, the free encyclopedia
The TBP-associated factors (TAF) are proteins that associate with the TATA-binding protein in transcription initiation. It is a part of the transcription initiation factor TFIID multimeric protein complex. It also makes up many other factors, including SL1. They mediate the formation of the transcription preinitiation complex, a step preceding transcription of DNA to RNA by RNA polymerase II.
TAFs have a signature N-terminal histone-like fold domain (HFD).[1] This domain is implicated in the pairwise interaction among specific TAFs.[2]
Function
TFIID
TFIID plays a central role in mediating promoter responses to various activators and repressors. It binds tightly to TAFII-250 and directly interacts with TAFII-40. TFIID is composed of TATA binding protein (TBP) and a number of TBP-associated factors (TAFS).[3]
TAF is part of the TFIID complex, and interacts with the following:
- Specific transcriptional activators
- Basal transcription factors
- Other TAFIIs
- Specific DNA sequences, for example the downstream promoter element or gene-specific core promoter sequence
Due to such interactions, they contribute transcription activation and to promoter selectivity.[3]
Some pairs of TAF interact with each other to form "lobes" in TFIID. Pairs known or suggested to exist in TFIID include TAF6-TAF9, TAF4-TAF12, TAF11-13, TAF8-TAF10 and TAF3-TAF10.[2]
SL1
Selective factor 1 is composed of the TATA-binding protein and three TAF (TATA box-binding protein-associated factor) subunits (TAF1A, TAF1B, and TAF1C). These TAFs do not have a histone-like fold domain.[4]
Other complexes
TAF is a part of SAGA (SPT-ADA-GCN5 acetylase) and related coactivation complexes.[2] Such complexes acetylate histone tails to activate genes.[5] Human has three SAGA-like complexes: PCAF, TFTC (TBP-free TAF-containing complex), and STAGA (SPT3-TAF9-GCN5L acetylase). PCAF (GCN5) and KAT2A (GCN5L) are two human homologs of the yeast Gcn5.[6]
TAF8, TAF10, and SPT7L forms a small TAF complex called SMAT.[2]
Structure
The N-terminal domain of TAF has a histone-like protein fold. It contains two short alpha helices and a long central alpha helix.[1]
Human genes
Assorted signatures
TAF domains are spread out across many digital signatures:
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