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Journal of Bacteriology, July 2008, p. 4736-4748, Vol. 190, No. 13
0021-9193/08/$08.00+0     doi:10.1128/JB.00089-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Integration Host Factor Positively Regulates Virulence Gene Expression in Vibrio cholerae{triangledown}

Emily Stonehouse, Gabriela Kovacikova, Ronald K. Taylor, and Karen Skorupski*

Department of Microbiology and Immunology, Dartmouth Medical School, Hanover, New Hampshire 03755

Received 17 January 2008/ Accepted 25 April 2008

Virulence gene expression in Vibrio cholerae is dependent upon a complex transcriptional cascade that is influenced by both specific and global regulators in response to environmental stimuli. Here, we report that the global regulator integration host factor (IHF) positively affects virulence gene expression in V. cholerae. Inactivation of ihfA and ihfB, the genes encoding the IHF subunits, decreased the expression levels of the two main virulence factors tcpA and ctx and prevented toxin-coregulated pilus and cholera toxin production. IHF was found to directly bind to and bend the tcpA promoter region at an IHF consensus site centered at position –162 by using gel mobility shift assays and DNase I footprinting experiments. Deletion or mutation of the tcpA IHF consensus site resulted in the loss of IHF binding and additionally disrupted the binding of the repressor H-NS. DNase I footprinting revealed that H-NS protection overlaps with both the IHF and the ToxT binding sites at the tcpA promoter. In addition, disruption of ihfA in an hns or toxT mutant background had no effect on tcpA expression. These results suggest that IHF may function at the tcpA promoter to alleviate H-NS repression.

* Corresponding author. Mailing address: Department of Microbiology and Immunology, HB7550, Dartmouth Medical School, Hanover, NH 03755. Phone: (603) 650-1634. Fax: (603) 650-1318. E-mail: Karen.A.Skorupski{at}Dartmouth.edu

{triangledown} Published ahead of print on 2 May 2008.

Journal of Bacteriology, July 2008, p. 4736-4748, Vol. 190, No. 13
0021-9193/08/$08.00+0     doi:10.1128/JB.00089-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

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  • Morash, M. G., Brassinga, A. K. C., Warthan, M., Gourabathini, P., Garduno, R. A., Goodman, S. D., Hoffman, P. S. (2009). Reciprocal Expression of Integration Host Factor and HU in the Developmental Cycle and Infectivity of Legionella pneumophila. Appl. Environ. Microbiol. 75: 1826-1837 [Abstract] [Full Text]  


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