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Journal of Bacteriology, January 2007, p. 142-150, Vol. 189, No. 1
0021-9193/07/$08.00+0     doi:10.1128/JB.01115-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Transcriptional Regulation of the yghJ-pppA-yghG-gspCDEFGHIJKLM Cluster, Encoding the Type II Secretion Pathway in Enterotoxigenic Escherichia coli{triangledown}

Ji Yang, Deborah L. Baldi, Marija Tauschek, Richard A. Strugnell, and Roy M. Robins-Browne*

Department of Microbiology and Immunology, University of Melbourne, Victoria 3010, and Murdoch Childrens Research Institute, Royal Children's Hospital, Parkville, Victoria 3052, Australia

Received 26 July 2006/ Accepted 19 October 2006

The gene cluster gspCDEFGHIJKLM codes for various structural components of the type II secretion pathway which is responsible for the secretion of heat-labile enterotoxin by enterotoxigenic Escherichia coli (ETEC). In this work, we used a variety of molecular approaches to elucidate the transcriptional organization of the ETEC type II secretion system and to unravel the mechanisms by which the expression of these genes is controlled. We showed that the gspCDEFGHIJKLM cluster and three other upstream genes, yghJ, pppA, and yghG, are cotranscribed and that a promoter located in the upstream region of yghJ plays a major role in the expression of this 14-gene transcriptional unit. Transcription of the yghJ promoter was repressed 168-fold upon a temperature downshift from 37°C to 22°C. This temperature-induced repression was mediated by the global regulatory proteins H-NS and StpA. Deletion mutagenesis showed that the promoter region encompassing positions –321 to +301 relative to the start site of transcription of yghJ was required for full repression. The yghJ promoter region is predicted to be highly curved and bound H-NS or StpA directly. The binding of H-NS or StpA blocked transcription initiation by inhibiting promoter open complex formation. Unraveling the mechanisms of regulation of type II secretion by ETEC enhances our understanding of the pathogenesis of ETEC and other pathogenic varieties of E. coli.

* Corresponding author. Mailing address: Department of Microbiology and Immunology, University of Melbourne, Victoria 3010, Australia. Phone: 61 3 8344 8275. Fax: 61 3 8344 8276. E-mail: r.browne{at}unimelb.edu.au.

{triangledown} Published ahead of print on 3 November 2006.

Journal of Bacteriology, January 2007, p. 142-150, Vol. 189, No. 1
0021-9193/07/$08.00+0     doi:10.1128/JB.01115-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

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