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Mol. Cell. Biol., Dec 1997, 6794-6802, Vol 17, No. 12
S Chou and K Struhl
Biochemical experiments indicate that the general transcription factor IIB
(TFIIB) can interact directly with acidic activation domains and that
activators can stimulate transcription by increasing recruitment of TFIIB
to promoters. For promoters at which recruitment of TFIIB to promoters is
limiting in vivo, one would predict that transcriptional activity should be
particularly sensitive to TFIIB mutations that decrease the association of
TFIIB with promoter DNA and/or with activation domains; i.e., such TFIIB
mutations should exacerbate a limiting step that occurs in wild-type cells.
Here, we describe mutations on the DNA-binding surface of TFIIB that
severely affect both TATA-binding protein (TBP)-TFIIB-TATA complex
formation and interaction with the VP16 activation domain in vitro. These
TFIIB mutations affect the stability of the TBP-TFIIB-TATA complex in vivo
because they are synthetically lethal in combination with TBP mutants
impaired for TFIIB binding. Interestingly, these TFIIB derivatives support
viability, and they efficiently respond to Gal4-VP16 and natural acidic
activators in different promoter contexts. These results suggest that in
vivo, recruitment of TFIIB is not generally a limiting step for acidic
activators. However, one TFIIB derivative shows reduced transcription of
GAL4, suggesting that TFIIB may be limiting at a subset of promoters in
vivo.
Copyright © 1997, American Society for Microbiology
Transcriptional activation by TFIIB mutants that are severely impaired in interaction with promoter DNA and acidic activation domains
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA.
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