Interplay of global regulators and cell physiology in the general stress response of Escherichia coli

Under Various stress conditions, two sigma subunits of RNA polymerase, sigm a(S) and sigma(70), coexist in Escherichia coli cells. In contrast to sigma (70), sigma(S) is subject to intricate regulation and coordinates an emerge ncy reaction to stress as well as long term stress adaptation. In vivo, the two sigma factors clearly control different genes. Yet, they are structura lly and functionally very similar and basically recognize the same promoter sequences. Recent data suggest that sigma factor specificity at stress-act ivated promoters is affected by the interplay of the two RNA polymerase hol oenzymes with additional regulatory factors, such as H-NS, Lrp, CRP, IHF or Fis, that differentially affect transcription initiation by sigma(S) or si gma(70) in a promoter-specific manner.