Importance of stereospecific positioning of the upstream cis-acting DNA element containing a curved DNA structure for the functioning of the Escherichia coli proV promoter.

The mechanism by which the Escherichia coli proV promoter is activated more than 100-fold in response to the medium osmolarity, without the help of any known trans-acting activators, is not yet fully understood. In this context, it has recently begun to be realized that structural features, not the primary sequences, of cis-acting DNA elements may be important for transcriptional regulation in prokaryotes. From this point of view, in this study the proV promoter was characterized by constructing a series of spacer-insertion mutants in a proV-lacZ fusion on the chromosome. Here it was found that the upstream cis-acting sequence must be positioned stereospecifically with respect to the principal -35 and -10 regions for the proV promoter to be fully activated. In this regard, it was suggested that an overall DNA structure, particularly DNA curvature, is an important cis-acting parameter for activation of the proV promoter.