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

• Published in: Journal of Bacteriology Vol. 194; no. 5; pp. 1205 - 1215
• Main Authors: Wang, Hongxia, Ayala, Julio C, Benitez, Jorge A, Silva, Anisia J
• Format: Journal Article
• Language: English
• Published: Washington, DC American Society for Microbiology 01.03.2012
• Subjects: bacteria; Bacterial proteins; Bacterial Proteins - metabolism; Bacteriology; Biological and medical sciences; Cholera; chromatin; Chromatin Immunoprecipitation; Diarrhea; DNA, Bacterial - metabolism; DNA-Binding Proteins - metabolism; DNA-directed RNA polymerase; Fundamental and applied biological sciences. Psychology; Gene expression; Gene Expression Profiling; Gene Expression Regulation, Bacterial; hemagglutinins; Humans; Locomotion; Metalloendopeptidases - biosynthesis; Microbiology; Miscellaneous; pathogens; precipitin tests; promoter regions; Promoter Regions, Genetic; Proteases; Protein Binding; Protein Interaction Mapping; proteinases; regulatory proteins; Sigma Factor - metabolism; Small intestine; stress response; Toxins; transcription (genetics); Transcription, Genetic; Vibrio cholerae; Vibrio cholerae - genetics; Vibrio cholerae - physiology; Peptidases; Regulation(control); Motility; Enzyme; Hemagglutinin; Vibrio cholerae; Bacteria; Hydrolases; Vibrionaceae; Histone; Protein; Stress
• ISSN: 0021-9193; 1098-5530; 1067-8832
• DOI: 10.1128/JB.05900-11

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 σS 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.