PHOP-SIMILAR-TO-P AND RNA-POLYMERASE SIGMA(A) HOLOENZYME ARE SUFFICIENT FOR TRANSCRIPTION OF PHO REGULON PROMOTERS IN BACILLUS-SUBTILIS - PHOP-SIMILAR-TO-P ACTIVATOR SITES WITHIN THE CODING REGION STIMULATE TRANSCRIPTION IN-VITRO

The Bacillus subtilis pstS operon and phoA gene are members of the Pho regulon that is controlled by PhoR, a histidine kinase, and PhoP, a r esponse regulator. Footprinting analysis showed that phosphorylated Ph oP extended the PhoP protected region in pstS and phoA promoters, and also bound to a separate site within the coding region of each gene. O ur previous in vivo studies have shown that, in contrast to other Pho regulon promoters that are not expressed in either phoP or phoR mutant s, a low-level induction from the pstS promoter (25% of parent strain) can be detected in a phoR mutant. In this study, by using an in vitro transcription system, we demonstrate that (i) only phosphorylated Pho P is a transcriptional activator of the pstS operon and of the phoA ge ne; (ii) phosphorylated PhoP and RNA polymerase sigma(A) holoenzyme ar e sufficient for in vitro transcription of the pstS promoter and the p hoA promoter; (iii) the activation of the pstS promoter requires lower concentrations of phosphorylated PhoP than does the phoA promoter for transcription; and (iv) PhoP binding sites in both the pstS promoter core binding region and in the 5' coding region of the gene, which hav e been identified by footprinting analysis, are important for the tran scription of the pstS promoter in vitro.