Interaction of the histone-like nucleoid structuring protein and the general stress response regulator RpoS at Vibrio cholerae promoters that regulate motility and hemagglutinin/protease expression

J Bacteriol. 2012 Mar;194(5):1205-15. doi: 10.1128/JB.05900-11. Epub 2011 Dec 22.

Abstract

The bacterium Vibrio cholerae colonizes the human small intestine and secretes cholera toxin (CT) to cause the rice-watery diarrhea characteristic of this illness. The ability of this pathogen to colonize the small bowel, express CT, and return to the aquatic environment is controlled by a complex network of regulatory proteins. Two global regulators that participate in this process are the histone-like nucleoid structuring protein (H-NS) and the general stress response regulator RpoS. In this study, we address the role of RpoS and H-NS in the coordinate regulation of motility and hemagglutinin (HA)/protease expression. In addition to initiating transcription of hapA encoding HA/protease, RpoS enhanced flrA and rpoN transcription to increase motility. In contrast, H-NS was found to bind to the flrA, rpoN, and hapA promoters and represses their expression. The strength of H-NS repression at the above-mentioned promoters was weaker for hapA, which exhibited the strongest RpoS dependency, suggesting that transcription initiation by RNA polymerase containing σ(S) could be more resistant to H-NS repression. Occupancy of the flrA and hapA promoters by H-NS was demonstrated by chromatin immunoprecipitation (ChIP). We show that the expression of RpoS in the stationary phase significantly diminished H-NS promoter occupancy. Furthermore, RpoS enhanced the transcription of integration host factor (IHF), which positively affected the expression of flrA and rpoN by diminishing the occupancy of H-NS at these promoters. Altogether, we propose a model for RpoS regulation of motility gene expression that involves (i) attenuation of H-NS repression by IHF and (ii) RpoS-dependent transcription initiation resistant to H-NS.

Publication types

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

MeSH terms

  • Bacterial Proteins / metabolism*
  • Chromatin Immunoprecipitation
  • DNA, Bacterial / metabolism
  • DNA-Binding Proteins / metabolism*
  • Gene Expression Profiling
  • Gene Expression Regulation, Bacterial*
  • Humans
  • Locomotion*
  • Metalloendopeptidases / biosynthesis*
  • Promoter Regions, Genetic
  • Protein Binding
  • Protein Interaction Mapping*
  • Sigma Factor / metabolism*
  • Transcription, Genetic
  • Vibrio cholerae / genetics
  • Vibrio cholerae / physiology*

Substances

  • Bacterial Proteins
  • DNA, Bacterial
  • DNA-Binding Proteins
  • H-NS protein, bacteria
  • Sigma Factor
  • sigma factor KatF protein, Bacteria
  • Metalloendopeptidases
  • hemagglutinin-protease