Identification of the sigma E subunit of Escherichia coli RNA polymerase: a second alternate sigma factor involved in high-temperature gene expression

Genes Dev. 1989 Sep;3(9):1462-71. doi: 10.1101/gad.3.9.1462.


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.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Bacterial Proteins / metabolism*
  • Base Sequence
  • Escherichia coli / genetics
  • Escherichia coli / metabolism*
  • Gene Expression Regulation
  • Genes, Bacterial
  • Hot Temperature
  • Molecular Sequence Data
  • Promoter Regions, Genetic
  • RNA Polymerase I / metabolism*
  • Sigma Factor / isolation & purification*
  • Transcription Factors / isolation & purification*
  • Transcription, Genetic


  • Bacterial Proteins
  • Sigma Factor
  • Transcription Factors
  • RNA Polymerase I