The global repressor FliZ antagonizes gene expression by ?S-containing RNA polymerase due to overlapping DNA binding specificity.

ABSTRACT: FliZ, a global regulatory protein under the control of the flagellar master regulator FlhDC, was shown to antagonize ?(S)-dependent gene expression in Escherichia coli. Thereby it plays a pivotal role in the decision between alternative life-styles, i.e. FlhDC-controlled flagellum-based motility or ?(S)-dependent curli fimbriae-mediated adhesion and biofilm formation. Here, we show that FliZ is an abundant DNA-binding protein that inhibits gene expression mediated by ?(S) by recognizing operator sequences that resemble the -10 region of ?(S)-dependent promoters. FliZ does so with a structural element that is similar to region 3.0 of ?(S). Within this element, R108 in FliZ corresponds to K173 in ?(S), which contacts a conserved cytosine at the -13 promoter position that is specific for ?(S)-dependent promoters. R108 as well as C(-13) are also crucial for DNA binding by FliZ. However, while a number of FliZ binding sites correspond to known ?(S)-dependent promoters, promoter activity is not a prerequisite for FliZ binding and repressor function. Thus, we demonstrate that FliZ also feedback-controls flagellar gene expression by binding to a site in the flhDC control region that shows similarity only to a -10 element of a ?(S)-dependent promoter, but does not function as a promoter.

SUBMITTER: Pesavento C 

PROVIDER: S-EPMC3367168 | biostudies-literature | 2012 Jun

REPOSITORIES: biostudies-literature