Identification of the sigma E subunit of Escherichia coli RNA polymerase: a second alternate sigma factor involved in high-temperature gene expression.
The rpoH gene of Escherichia coli encodes sigma 32, the 32-kD sigma-factor responsible for the heat-inducible transcription of the heat shock genes. rpoH is transcribed from at least three promoters. Two of these promoters are recognized by RNA polymerase containing sigma 70, the predominant sigma-factor. We purified the factor responsible for recognizing the third rpoH promoter (rpoH P3) and identified it as RNA polymerase containing a novel sigma-factor with an apparent Mr of 24,000. This new sigma, which we call sigma E, is distinct from the known sigma factors in molecular weight and promoter specificity. sigma E holoenzyme will not recognize the sigma 70- or sigma 32-controlled promoters we tested, but it does transcribe the htrA gene, which is required for viability at temperatures greater than 42 degrees C. The in vivo role of sigma E is not known. The transcripts from the sigma E-controlled rpoH P3 and htrA promoters are most abundant at very high temperature, suggesting the sigma E holoenzyme may transcribe a second set of heat-inducible genes that are involved in growth at high temperature or in thermotolerance.
Erickson
J W
JW
Department of Bacteriology, University of Wisconsin, Madison 53706.
Gross
C A
CA
D001426:Bacterial Proteins / Q000378:metabolism*; D001483:Base Sequence; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D005798:Genes, Bacterial; D006358:Hot Temperature; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D012318:RNA Polymerase I / Q000378:metabolism*; D012808:Sigma Factor / Q000302:isolation & purification*; D014157:Transcription Factors / Q000302:isolation & purification*; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D012808:Sigma Factor; D014157:Transcription Factors; D012318:RNA Polymerase I