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Mol. Cell. Biol., 09 1995, 4683-4693, Vol 15, No. 9
RJ Austin and MD Biggin
We examined the mechanism by which the C-terminal 236 amino acids of the
even-skipped protein (region CD) repress transcription. A fusion protein,
CDGB, was created that contains region CD fused to the glucocorticoid
receptor DNA binding domain. This protein repressed transcription in an in
vitro system containing purified fractions of the RNA polymerase II general
transcription factors, and repression was dependent upon the presence of
high-affinity glucocorticoid receptor binding sites in the promoter.
Repression by CDGB was prevented when the promoter DNA was preincubated
with TFIID or TBP, whereas preincubation of the template DNA with CDGB
prevented TFIID binding. Together, these results strongly imply that CDGB
represses transcription by inhibiting TFIID binding, and further
experiments suggested a mechanism by which this may occur. Region CD can
mediate cooperative interactions between repressor molecules such that
molecules bound at the glucocorticoid receptor binding sites stabilize
binding of additional CDGB molecules to low-affinity binding sites
throughout the basal promoter. Binding to some of these low-affinity sites
was shown to contribute to repression. Further experiments suggested that
the full-length eve protein also represses transcription by the same
mechanism. We speculate that occupancy of secondary sites within the basal
promoter by CDGB or the eve protein inhibits subsequent TFIID binding to
repress transcription, a mechanism we term cooperative blocking.
Copyright © 1995, American Society for Microbiology
A domain of the even-skipped protein represses transcription by preventing TFIID binding to a promoter: repression by cooperative blocking
Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, USA.
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