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 pl...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2000-03, Vol.97 (7), p.3538-3543
Main Authors: Servant, Pascale, Grandvalet, Cosette, Mazodier, Philippe
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Bacteria
Bacterial Proteins
Base Sequence
Biochemistry, Molecular Biology
Biological Sciences
Circular Dichroism
DNA
DNA, Bacterial
Gels
Genes
Heat-Shock Proteins - physiology
Heat-Shock Response
High temperature
Life Sciences
Microbiology
Molecular Sequence Data
Oligonucleotides
Promoter regions
Promoter Regions, Genetic
Protein Conformation
Proteins
Repetitive Sequences, Nucleic Acid
Repressor Proteins - chemistry
Repressor Proteins - genetics
Repressor Proteins - physiology
Rheas
Shock heating
Spectroscopy
Streptomyces - physiology
Temperature
Thermoregulation
Transcription, Genetic
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Summary: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 foot-printing 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.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.97.7.3538