The htpR gene product of E. coli is a sigma factor for heat-shock promoters
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The htpR gene of E. coli encodes a positive regulator of the heat-shock response. We have fused the htpR gene to the inducible PL promoter of phage lambda. Overproduction of HtpR following a temperature upshift resulted in the overexpression of heat-shock proteins. We describe the purification and initial in vitro characterization of the factor controlling expression of heat-shock genes. The factor was the 32 kd htpR gene product. In vitro, a mixture of HtpR and core RNA polymerase initiated transcription at heat-shock promoters. The sigma factor encoded by rpoD was not required for this reaction. Therefore, HtpR is a sigma factor that promotes transcription initiation at heat-shock promoters. We propose that htpR be renamed rpoH and that the gene product be called sigma-32.
author list (cited authors)
Grossman, A. D., Erickson, J. W., & Gross, C. A.