title: 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.
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.
authors.affiliation: Southern Research Institute, Drug Discovery Division, Department of Biochemistry and Molecular Biology, Birmingham, Alabama, USA.
authors.forename: Hongxia
authors.initials: H
authors.lastname: Wang
authors.forename: Julio C
authors.initials: JC
authors.lastname: Ayala
authors.forename: Jorge A
authors.initials: JA
authors.lastname: Benitez
authors.forename: Anisia J
authors.initials: AJ
authors.lastname: Silva
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D047369:Chromatin Immunoprecipitation; D004269:DNA, Bacterial / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D008124:Locomotion; D008666:Metalloendopeptidases / Q000096:biosynthesis*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D025941:Protein Interaction Mapping; D012808:Sigma Factor / Q000378:metabolism*; D014158:Transcription, Genetic; D014734:Vibrio cholerae / Q000235:genetics / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; C031908:H-NS protein, bacteria; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria; D008666:Metalloendopeptidases; C039814:hemagglutinin-protease