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Dual Control of Helicobacter pylori Heat Shock Gene Transcription by HspR and HrcA. Gunther Spohn, 2004.The HspR repressor regulates transcription of the groESL, hrcA-grpE-dnaK, and cbpA-hspR-orf operons of Helicobacter pylori . Here we show that two of the HspR-regulated operons, namely, the groESL and dnaK operons, encoding the major cellular chaperone machineries are also regulated by the H . pylori homologue of the HrcA repressor . Similarly to the hspR mutation, deletion of the hrcA gene also leads to complete derepression of the Pgro and Phrc promoters . The presence of both HspR and HrcA is therefore necessary for regulated transcription from these promoters . HrcA binds directly to Pgro and Phrc, likely contacting two inverted repeats with similarity to the CIRCE motif, which are present on both promoters . HrcA regulation is, however, shown to depend on binding of the HspR protein, since deletion of the HspR-binding site of the Pgro promoter leads to loss of heat inducibility of this promoter . In contrast, transcription from the Pcbp promoter is regulated solely by HspR . HspR is also shown to form oligomers in vivo through a stretch of hydrophobic repeats between amino acid positions 66 and 97 . The implications of these findings for the elucidation of the networks regulating heat shock gene expression in H . pylori are discussed .
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