Regulation of bacterial RNA polymerase sigma factor activity: a structural perspective

Curr Opin Microbiol. 2008 Apr;11(2):121-7. doi: 10.1016/j.mib.2008.02.016. Epub 2008 Mar 28.


In bacteria, sigma factors are essential for the promoter DNA-binding specificity of RNA polymerase. The sigma factors themselves are regulated by anti-sigma factors that bind and inhibit their cognate sigma factor, and 'appropriators' that deploy a particular sigma-associated RNA polymerase to a specific promoter class. Adding to the complexity is the regulation of anti-sigma factors by both anti-anti-sigma factors, which turn on sigma factor activity, and co-anti-sigma factors that act in concert with their partner anti-sigma factor to inhibit or redirect sigma activity. While sigma factor structure and function are highly conserved, recent results highlight the diversity of structures and mechanisms that bacteria use to regulate sigma factor activity, reflecting the diversity of environmental cues that the bacterial transcription system has evolved to respond.

Publication types

  • Research Support, N.I.H., Extramural
  • Review

MeSH terms

  • Amino Acid Sequence
  • Bacteria / genetics
  • Bacteria / metabolism*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • DNA-Directed RNA Polymerases / antagonists & inhibitors
  • DNA-Directed RNA Polymerases / chemistry*
  • DNA-Directed RNA Polymerases / metabolism*
  • Gene Expression Regulation, Bacterial*
  • Models, Molecular
  • Molecular Sequence Data
  • Sigma Factor / antagonists & inhibitors
  • Sigma Factor / chemistry*
  • Sigma Factor / metabolism*
  • Structure-Activity Relationship


  • Bacterial Proteins
  • Sigma Factor
  • RNA polymerase sigma 70
  • DNA-Directed RNA Polymerases