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Cells lacking ClpB display a prolonged shutoff phase of the heat shock response in Caulobacter crescentus
Author(s) -
Simão Rita C. G.,
Susin Michelle F.,
AlvarezMartinez Cristina E.,
Gomes Suely L.
Publication year - 2005
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2005.04713.x
Subject(s) - clpb , caulobacter crescentus , sigma factor , biology , heat shock , heat shock protein , mutant , chaperone (clinical) , rna polymerase , transcription (linguistics) , microbiology and biotechnology , escherichia coli , gene , biochemistry , cell cycle , medicine , linguistics , philosophy , pathology
Summary The heat shock response in Caulobacter crescentus was previously shown to be positively regulated by the alternative sigma factor of RNA polymerase (RNAP) σ 32 , and negatively modulated by DnaK during the induction phase of the heat shock response but not during the recovery phase. In the present work we have investigated the involvement of the chaperone ClpB in the control of the heat shock response in C. crescentus . Data obtained indicated a role of ClpB in downregulation of heat shock protein (HSP) synthesis, as cells lacking this chaperone showed a prolonged shutoff phase of the heat shock response. In Escherichia coli , it has been proposed that the DnaK chaperone system switches transcription back to constitutively expressed genes through simultaneous reactivation of heat‐aggregated σ 70 , as well as sequestration of σ 32 away from RNAP. In C. crescentus , results obtained with a clpB null mutant indicate that ClpB could be involved in the reactivation of the major sigma factor σ 73 . In support of this hypothesis, we showed that transcription directed from σ 73 ‐dependent promoters is not switched back in the clpB null mutant during the recovery phase. Furthermore, we observed that resolubilization of heat‐aggregated σ 73 is dependent on the presence of ClpB. Our findings also indicated that the absence of ClpB made cells more sensitive to heat shock and ethanol but not to other stresses, and unable to acquire thermotolerance.