Transcription factor TFIID

TAF 250 TBP-Associated Factor II 250. Another direct connection between acetylation and transcriptional activation was demonstrated with the discovery that one of the TAFII (TATA-binding protein [TBP]-associated factor) subunits of the general transcription factor TFIID is itself a HAT. TFIID is one of the general factors required for the assembly of the RNA polymerase II transcription preinitiation... 

Requires sigma (a) to initiate at a promoter No sigma, but transcription factors (TFIID) bind before RNA polymerase... 

In eukaryotes, general transcription factors must bind to the promoter to allow RNA polymerase II to bind and form the initiation complex at the start site for transcription. General manscription factors are common to most genes. The general transcription factor TFIID (the TATA fector) must bind to the TATA box before RNA polymerase II can bind. Other examples delude SP-1 and NF-.l that modulate basal transcription of many genes. 

The best-characterized coactivator is the transcription factor TFIID (Fig. 28-27). In eukaryotes, TFIID is a large complex that includes TBP and ten or more TBP-associated factors (TAFs). Some TAFs resemble histones and may play a role in displacing nucleosomes during the activation of transcription. Many DNA-binding transactivators aid in transcription initiation by interacting with one or more TAFs. The requirement for TAFs to initiate transcription can vary greatly from one gene to another. Some promoters require TFIID, some do not, and some require only subsets of the TFIID TAF subunits. 

M. Horikoshi, et al. Transcription factor TFIID induces DNA bending upon binding to the TATA element Proc Natl Acad Sci U S A 89 (1992) 1060-4. 

P.A. Emanuel and D.S. Gilmour. Transcription factor TFIID recognizes DNA sequences downstream of the TATA element in the Hsp70 heat shock gene. Proc. Natl. Acad. Sci. USA 90 (1993) 8449-53. 

TATA box. A sequence found in the promoter (part of the 5 flanking region) of many genes. Deletion of this site (the binding site of transcription factor TFIID) causes a marked reduction in transcription, and gives rise to heterogeneous transcription initiation sites. 

Promoters. The promoter sequences in eukaryotic DNA are larger, more complicated, and more variable than those of prokaryotes. Many promoters for RNA polymerase II contain consensus sequences, referred to as the TATA box, which occur about 25-30 bp upstream from the transcription initiation site. As illustrated in Figure 18.23, the binding of the transcription factor TFIID to the... 

TFIIA, TFIIB, TFIID, TFIIE, TFIIF, and TFIIH are the general transcription factors. TFIID is also the TATA-box binding protein and is associated with TAFs (TBP associated factors). 

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