title: The htpR gene product of E. coli is a sigma factor for heat-shock promoters.
abstract: 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.
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D012321:DNA-Directed RNA Polymerases / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics*; D005786:Gene Expression Regulation; D005798:Genes, Bacterial; D006360:Heat-Shock Proteins / Q000235:genetics*; D008970:Molecular Weight; D009876:Operon; D012808:Sigma Factor / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics*; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D006360:Heat-Shock Proteins; D012808:Sigma Factor; D014157:Transcription Factors; D012321:DNA-Directed RNA Polymerases