The RheA repressor is the thermosensor of the HSP18 heat shock response in Streptomyces albus.
Microorganisms have mechanisms to sense their environment and rapidly adapt to survive changes in conditions. In Streptomyces albus, various transcriptional repressors mediate the induction of heat shock genes. The RheA repressor regulates the synthesis of HSP18, a small heat shock protein, which plays a role in thermotolerance. The RheA protein was purified to determine how it responds rapidly to temperature. Gel retardation assays and footprinting experiments identified the specific target of RheA as an inverted repeat (TGTCATC 5N GATGACA) located in Phsp18, PrheA which is the common promoter region of the divergon. Gel retardation assays detected RheA-complexes formed with the hsp18-rheA promoters. The complexes did not form at higher temperature. In vitro transcription experiments showed that RheA is an autoregulatory protein and that its activity is inhibited by high temperature. The temperature-induced derepression by RheA is reversible. Dichroism circular spectroscopy revealed a reversible change of RheA conformation in relation with the temperature that could represent a transition between an active and an inactive form. Our experiments demonstrate that RheA acts as a cellular thermometer in hsp18 regulation.
Servant
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Unité de Biochimie Microbienne, Institut Pasteur, 25, rue du Docteur Roux, 75724 Paris Cedex 15, France.
Grandvalet
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Mazodier
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D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D001483:Base Sequence; D002942:Circular Dichroism; D004269:DNA, Bacterial; D006360:Heat-Shock Proteins / Q000502:physiology*; D018869:Heat-Shock Response; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D011487:Protein Conformation; D012091:Repetitive Sequences, Nucleic Acid; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D013302:Streptomyces / Q000502:physiology*; D013696:Temperature; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D006360:Heat-Shock Proteins; D012097:Repressor Proteins; C406736:RheA protein, Streptomyces albus; C081475:hsp18 protein, bacteria