TBP-associated factor

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.

TBP associated factor (TAF6)
drosophila dtafii42/dtafii62 (like TAF6/TAF9) heterotetramer, HFD
Identifiers
Symbol	TAF
Pfam	PF02969
Pfam clan	CL0012
InterPro	IPR004823
SCOP2	1bh9 / SCOPe / SUPFAM
Available protein structures: Pfam   structures / ECOD   PDB RCSB PDB; PDBe; PDBj PDBsum structure summary

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

• TAF1 (TAFII250)
• TAF2 (CIF150)
• TAF3 (TAFII140)
• TAF4 (TAFII130/135)
• TAF4B (TAFII105)
• TAF5 (TAFII100)
• TAF6 (TAFII70/80)
  • TAF6L (PAF65A)
• TAF7 (TAFII55)
• TAF8 (TAFII43)
• TAF9 (TAFII31/32)
• TAF9B (TAFII31L)
• TAF10 (TAFII30)
• TAF11 (TAFII28)
• TAF12 (TAFII20/15)
• TAF13 (TAFII18)
• TAF15 (TAFII68)

Assorted signatures

TAF domains are spread out across many digital signatures:

TAF4 Identifiers Symbol TAF4 Pfam PF05236 InterPro IPR007900 Available protein structures: Pfam   structures / ECOD   PDB RCSB PDB; PDBe; PDBj PDBsum structure summary

TAF Identifiers Symbol ? Pfam PF04719 Available protein structures: Pfam   structures / ECOD   PDB RCSB PDB; PDBe; PDBj PDBsum structure summary

TAF13 Identifiers Symbol TFIID-18kDa Pfam PF02269 InterPro IPR003195 Available protein structures: Pfam   structures / ECOD   PDB RCSB PDB; PDBe; PDBj PDBsum structure summary

TAFII31 (TAF9) Identifiers Symbol TFIID-31kDa Pfam PF02291 InterPro IPR003162 Available protein structures: Pfam   structures / ECOD   PDB RCSB PDB; PDBe; PDBj PDBsum structure summary

TAF Identifiers Symbol ? Pfam PF03847 Available protein structures: Pfam   structures / ECOD   PDB RCSB PDB; PDBe; PDBj PDBsum structure summary

TAF Identifiers Symbol ? Pfam PF03540 Available protein structures: Pfam   structures / ECOD   PDB RCSB PDB; PDBe; PDBj PDBsum structure summary

TAF/Nervy homology (TAF4/4B) Identifiers Symbol TAFH Pfam PF07531 InterPro IPR003894 SMART TAFH Available protein structures: Pfam   structures / ECOD   PDB RCSB PDB; PDBe; PDBj PDBsum structure summary

TAF RNA Polymerase I subunit A (TAF1A) Identifiers Symbol TAF1_subA Pfam PF14929 InterPro IPR039495 Available protein structures: Pfam   structures / ECOD   PDB RCSB PDB; PDBe; PDBj PDBsum structure summary