Characterization of the HspR-Mediated Stress Response inHelicobacter pylori

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Abstract
The major heat shock genes of Helicobacter pylori are regulated by the HspR repressor. In the present study we characterize the transcriptional response of the three known HspR-dependent promoters Pcbp, Pgro, and Phrc to different environmental stresses. A temperature shift from 37 to 42°C causes a typical heat shock response at all three promoters characterized by an immediate and strong induction phase of transcription and a subsequent adaptation phase, which is specific for each promoter and whose onset is determined partially by the half-lives of the respective mRNAs. Exposure to high osmolarity induces a similar response on the Pgro and Pcbp promoters while no such response is detectable at the Phrc promoter. Puromycin treatment induces transcription from all three HspR-dependent promoters, indicating that different environmental stresses are intracellularly sensed by the regulatory machinery through the accumulation of nonnative proteins. The implications of these data for the regulatory network controlling the heat shock response in H. pylori are discussed.