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Journal of Bacteriology, February 2004, p. 699-705, Vol. 186, No. 3
0021-9193/04/$08.00+0     DOI: 10.1128/JB.186.3.699-705.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Regulation of IcsP, the Outer Membrane Protease of the Shigella Actin Tail Assembly Protein IcsA, by Virulence Plasmid Regulators VirF and VirB

Helen J. Wing, Arthur W. Yan, Seth R. Goldman, and Marcia B. Goldberg*

Infectious Disease Division, Massachusetts General Hospital, Cambridge, Massachusetts 02139

Received 7 August 2003/ Accepted 31 October 2003

The Shigella outer membrane protease IcsP removes the actin assembly protein IcsA from the bacterial surface, and consequently modulates Shigella actin-based motility and cell-to-cell spread. Here, we demonstrate that IcsP expression is undetectable in mutants lacking either of two transcriptional activators, VirF and VirB. In wild-type Shigella spp., virB expression is entirely dependent on VirF; therefore, to circumvent this regulatory cascade, we independently expressed VirF or VirB in Shigella strains lacking both activators and measured both IcsP levels and transcription from the icsP promoter. Our results show that VirB significantly enhanced icsP transcription, even in the absence of VirF. In contrast, when VirF was induced in the absence of VirB, VirF had variable effects. The regulation of icsP is distinctly different from the regulation of the gene encoding its major substrate, icsA, which is activated by VirF and not VirB. We propose that the different pathways regulating icsA and icsP may be critical to the modulation of IcsA-mediated actin-based motility by IcsP.

* Corresponding author. Mailing address: University Park, 65 Landsdowne St., Cambridge, MA 02139. Phone: (617) 768-8740. Fax: (617) 768-8738. E-mail: mgoldberg1{at}partners.org.

Journal of Bacteriology, February 2004, p. 699-705, Vol. 186, No. 3
0021-9193/04/$08.00+0     DOI: 10.1128/JB.186.3.699-705.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Castellanos, M. I., Harrison, D. J., Smith, J. M., Labahn, S. K., Levy, K. M., Wing, H. J. (2009). VirB Alleviates H-NS Repression of the icsP Promoter in Shigella flexneri from Sites More Than One Kilobase Upstream of the Transcription Start Site. J. Bacteriol. 191: 4047-4050 [Abstract] [Full Text]  
  • Goldman, S. R., Tu, Y., Goldberg, M. B. (2008). Differential Regulation by Magnesium of the Two MsbB Paralogs of Shigella flexneri. J. Bacteriol. 190: 3526-3537 [Abstract] [Full Text]  
  • Gall, T. L., Mavris, M., Martino, M. C., Bernardini, M. L., Denamur, E., Parsot, C. (2005). Analysis of virulence plasmid gene expression defines three classes of effectors in the type III secretion system of Shigella flexneri. Microbiology 151: 951-962 [Abstract] [Full Text]  


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