ANALYSIS OF THE SPACER DNA BETWEEN THE CYCLIC-AMP RECEPTOR PROTEIN-BINDING SITE AND THE LAC PROMOTER

The role of the spacer region DNA between the cyclic AMP receptor prot ein (CRP) site and the RNA polymerase in the lac promoter was examined . We wanted to determine whether the wild-type DNA sequence of this re gion was an absolute requirement for CRP activation of inc transcripti on. The sequence of a 9-bp stretch of the spacer, from -41 to -49 rela tive to the start of transcription, was randomized, and the effect of randomization on inc expression was investigated in vitro and in vivo. We found that the spacer contains no specific sequence determinants f or CRP activation of lac transcription; fewer than 1% of the mutants d isplayed greater than a 50% decrease in CRP activation of lac transcri ption.