Negative regulation of the heat shock response in Streptomyces.
All organisms respond to a sudden increase in temperature by inducing the synthesis of a set of proteins called heat shock proteins (HSPs). Although the induction of HSPs is a universal response, a diversity of mechanisms control HSP synthesis in different organisms. In Streptomyces, the synthesis of major HSPs, such as the widespread molecular chaperones DnaK, ClpB, GroEL and HSP18, is negatively controlled at the transcriptional level by at least three different repressors. The control of groE gene expression involves an inverted repeat (called the CIRCE element) that is highly conserved among eubacteria, and the HrcA repressor. The dnaK operon and clpB belong to the HspR /HAIR regulon. The HspR repressor-HAIR operator system is used in some bacteria but is not widespread. In particular, it has not been found in gram-positive bacteria with low G+C content. Transcription of hsp18, which encodes a small HSP, is regulated by the RheA repressor. This repressor, which has intrinsic thermosensor activity, has to date been identified only in Streptomyces.
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Unité de Biochimie Microbienne, Institut Pasteur, 25 rue du Docteur Roux, 75724 Paris Cedex 15, France.
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D001426:Bacterial Proteins; D018835:Chaperonin 10 / Q000235:genetics; D018834:Chaperonin 60 / Q000235:genetics; D004268:DNA-Binding Proteins; D015964:Gene Expression Regulation, Bacterial; D006360:Heat-Shock Proteins / Q000235:genetics* / Q000502:physiology; D018869:Heat-Shock Response / Q000235:genetics; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism; D009876:Operon; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000502:physiology; D013302:Streptomyces / Q000235:genetics*
D001426:Bacterial Proteins; D018835:Chaperonin 10; D018834:Chaperonin 60; D004268:DNA-Binding Proteins; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D012097:Repressor Proteins