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Mol. Cell. Biol., Nov 1995, 6474-6478, Vol 15, No. 11
X Liu and AJ Berk
p53, the protein encoded by one of the most significant human tumor
suppressor genes, is a sequence-specific transcriptional activator. When
activated by a double-stranded DNA break, p53 function arrests cells in G1
and can induce apoptosis. Transcriptional activation function is critical
for p53 tumor suppression, although transcriptional repressing and
nontranscriptional functions of p53 may contribute. p53 activation requires
that it bind to TFIID through interactions with TATA box-binding protein
(TBP)-associated factors and potentially with TBP. Here, we studied the
mechanism of p53 activation using in vitro transcription and a sufficiently
high p53 concentration to squelch activated transcription. Squelching is
thought to result when target molecules that interact with activation
domains are titrated by binding to excess activator. Addition of either
excess TFIIB or TFIID but not other proteins required for p53-activated
transcription reversed squelching by high p53 concentrations, whereas
neither stimulated transcription in reactions without excess p53. These
results reveal that both TFIIB and TFIID are inhibited by high
concentrations of p53 and suggest that p53 activation may work through
direct or indirect interactions with both TFIIB and TFIID.
Copyright © 1995, American Society for Microbiology
Reversal of in vitro p53 squelching by both TFIIB and TFIID
Molecular Biology Institute, University of California, Los Angeles 90095-1570, USA.
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