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Journal of Bacteriology, November 2009, p. 6788-6795, Vol. 191, No. 22
0021-9193/09/$08.00+0     doi:10.1128/JB.00682-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Vibrio cholerae LexA Coordinates CTX Prophage Gene Expression{triangledown}

Harvey H. Kimsey and Matthew K. Waldor*

Channing Laboratory, Brigham and Women's Hospital, and Howard Hughes Medical Institute, Boston, Massachusetts 02115

Received 26 May 2009/ Accepted 1 August 2009

The filamentous bacteriophage CTX{Phi} transmits the cholera toxin genes by infecting and lysogenizing its host, Vibrio cholerae. CTX{Phi} genes required for virion production initiate transcription from the strong PA promoter, which is dually repressed in lysogens by the phage-encoded repressor RstR and the host-encoded SOS repressor LexA. Here we identify the neighboring divergent rstR promoter, PR, and show that RstR both positively and negatively autoregulates its own expression from this promoter. LexA is absolutely required for RstR-mediated activation of PR transcription. RstR autoactivation occurs when RstR is bound to an operator site centered 60 bp upstream of the start of transcription, and the coactivator LexA is bound to a 16-bp SOS box centered at position –23.5, within the PR spacer region. Our results indicate that LexA, when bound to its single site in the CTX{Phi} prophage, both represses transcription from PA and coactivates transcription from the divergent PR. We propose that LexA coordinates PA and PR prophage transcription in a gene regulatory circuit. This circuit is predicted to display transient switch behavior upon induction of CTX{Phi} lysogens.

* Corresponding author. Mailing address: Channing Laboratory, 181 Longwood Ave., Boston, MA 02115. Phone: (617) 525-4646. Fax: (617) 525-4660. E-mail: mwaldor{at}rics.bwh.harvard.edu

{triangledown} Published ahead of print on 7 August 2009.

Journal of Bacteriology, November 2009, p. 6788-6795, Vol. 191, No. 22
0021-9193/09/$08.00+0     doi:10.1128/JB.00682-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Related articles in JB:

A New Twist on a Classic Paradigm: Illumination of a Genetic Switch in Vibrio cholerae Phage CTX{Phi}
Bryce E. Nickels
JB 2009 191: 6779-6781. [Full Text]  



This article has been cited by other articles:

  • Nickels, B. E. (2009). A New Twist on a Classic Paradigm: Illumination of a Genetic Switch in Vibrio cholerae Phage CTX{Phi}. J. Bacteriol. 191: 6779-6781 [Full Text]  


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