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pubmed:abstractText |
TFIID recognizes multiple sequence elements in the hsp70 promoter of Drosophila. Here, we investigate the function of sequences downstream from the TATA element. A mutation in the initiator was identified that caused an eightfold reduction in binding of TFIID and a fourfold reduction in transcription in vitro. Another mutation in the +24 to +29 region was somewhat less inhibitory, but a mutation in the +14 to +19 region had essentially no effect. The normal promoter and the mutants in the initiator and the +24 to +29 region were transformed into flies by P element-mediated transformation. The initiator mutation reduced expression an average of twofold in adult flies, whereas the mutation in the +24 to +29 region had essentially no effect. In contrast, a promoter combining the two mutations was expressed an average of sixfold less than the wild type. The results suggest that the initiator and the +24 to +29 region could serve overlapping functions in vivo. Protein-DNA cross-linking was used to identify which subunits of TFIID contact the +24 to +29 region and the initiator. No specific subunits were found to cross-link to the +24 to +29 region. In contrast, the initiator cross-linked exclusively to dTAF230. Remarkably, dTAF230 cross-links approximately 10 times more efficiently to the nontranscribed strand than to the transcribed strand at the initiator.
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