DNA-BASED POSITIVE CONTROL MUTANTS IN THE BINDING-SITE SEQUENCE OF 434-REPRESSOR

As detected by chemical nuclease treatments, the conformation of the 4 34 repressor-DNA complex depends on the sequence of the bound DNA (Bel l, A. C., and Koudelka, G. B. (1993) J, Mel. Biol. 234, 542-553). We s how here that these DNA sequence-dependent conformational changes alte r the efficiency with which the repressor activates transcription from 434 P-RM. Several lines of evidence suggest that binding site sequenc e affects the repressor's ability to activate transcription by alterin g the accessibility of the activation surface on the repressor to RNA polymerase, The results presented here show that in addition to affect ing transcription by altering the overall binding affinity of protein for DNA, DNA sequence may also modulate the activity of the DNA-bound protein.