Corepressor required for adenovirus E1B 55,000-molecular-weight protein repression of basal transcription.
Adenovirus E1B 55,000-molecular-weight protein (55K) binds to host cell p53, stabilizing it, greatly increasing its affinity for its cognate DNA-binding site, and converting it from a regulated activator to a constitutive repressor. Here we analyzed the mechanism of repression by the p53-E1B 55K complex. E1B 55K repression requires that 55K be tethered to the promoter by binding directly to DNA-bound p53. Transcription from an assembled, p53-activated preinitiation complex was not repressed by the subsequent addition of E1B 55K, suggesting that either sites of 55K interaction with p53 or targets of 55K in the preinitiation complex are blocked. Specific E1B 55K repression was observed in reactions lacking TFIIA and with recombinant TATA-binding protein in place of TFIID, conditions under which p53 does not activate transcription. Thus, E1B 55K does not simply inhibit a p53-specific activation mechanism but rather blocks basal transcription. As a consequence, E1B 55K may repress transcription from any promoter with an associated p53-binding site, no matter what other activators associate with the promoter. E1B 55K did not repress basal transcription in reactions with recombinant and highly purified general transcription factors and RNA polymerase II but rather required a corepressor that copurifies with the polymerase.
Martin
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ME
Molecular Biology Institute and Department of Microbiology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California 90095-1570, USA.
Berk
A J
AJ
D017501:Adenovirus E1B Proteins / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000235:genetics; D012319:RNA Polymerase II / Q000235:genetics; D011994:Recombinant Proteins / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics*; D035181:TATA-Box Binding Protein; D035561:Transcription Factor TFIIA; D014157:Transcription Factors / Q000235:genetics; D014158:Transcription, Genetic / Q000235:genetics*; D016159:Tumor Suppressor Protein p53 / Q000235:genetics* / Q000378:metabolism
D017501:Adenovirus E1B Proteins; D004268:DNA-Binding Proteins; D011994:Recombinant Proteins; D012097:Repressor Proteins; D035181:TATA-Box Binding Protein; D035561:Transcription Factor TFIIA; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; D012319:RNA Polymerase II