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CcpA Causes Repression of the phoPR Promoter through a Novel Transcription Start Site, P_A6

Ankita Puri-Taneja, Salbi Paul, Yinghua Chen, and F. Marion Hulett^*

Laboratory for Molecular Biology, Department of Biological Sciences, University of Illinois at Chicago, Chicago, Illinois 60607

Received 25 August 2005/ Accepted 23 November 2005

The Bacillus subtilis PhoPR two-component system is directly responsible for activation or repression of Pho regulon genes in response to phosphate deprivation. The response regulator, PhoP, and the histidine kinase, PhoR, are encoded in a single operon with a complex promoter region that contains five known transcription start sites, which respond to at least two regulatory proteins. We report here the identification of another direct regulator of phoPR transcription, carbon catabolite protein A, CcpA. This regulator functions in the presence of glucose or other readily metabolized carbon sources. The maximum derepression of phoPR expression in a ccpA mutant compared to a wild-type stain was observed under excess phosphate conditions with glucose either throughout growth in a high-phosphate defined medium or in a low-phosphate defined medium during exponential growth, a growth condition when phoPR transcription is low in a wild-type strain due to the absence of autoinduction. Either HPr or Crh were sufficient to cause CcpA dependent repression of the phoPR promoter in vivo. A ptsH1 (Hpr) crh double mutant completely relieves phoPR repression during phosphate starvation but not during phosphate replete growth. In vivo and in vitro studies showed that CcpA repressed phoPR transcription by binding directly to the cre consensus sequence present in the promoter. Primer extension and in vitro transcription studies revealed that the CcpA regulation of phoPR transcription was due to repression of P_A6, a previously unidentified promoter positioned immediately upstream of the cre box. E^A was sufficient for transcription of P_A6, which was repressed by CcpA in vitro. These studies showed direct repression by CcpA of a newly discovered E^A-responsive phoPR promoter that required either Hpr or Crh in vivo for direct binding to the putative consensus cre sequence located between P_A6 and the five downstream promoters characterized previously.

Present address: Department of Medicine, Section of Hematology-Oncology, University of Chicago, Chicago, Ill.

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