Journal of Bacteriology, March 2004, p. 1620-1628, Vol. 186, No. 6
0021-9193/04/$08.00+0 DOI: 10.1128/JB.186.6.1620-1628.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.
Regulation of Escherichia coli Hemolysin E Expression by H-NS and Salmonella SlyA
Neil R. Wyborn, Melanie R. Stapleton, Valia A. Norte, Ruth E. Roberts, Jamie Grafton, and Jeffrey Green*
The Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield S10 2TN, United Kingdom
Received 30 June 2003/
Accepted 5 December 2003
The Escherichia coli hlyE gene (also known as clyA or sheA) codes for a novel pore-forming toxin. Previous work has shown that the global transcription factors FNR and CRP positively regulate hlyE expression by binding at the same site. Here in vivo transcription studies reveal that FNR occupies the hlyE promoter more frequently than CRP, providing a mechanism for the moderate upregulation of hlyE expression in response to two distinct environmental signals (oxygen and glucose starvation). It has been reported that H-NS interacts with two large regions of the hlyE promoter (PhlyE), one upstream of the -35 element and one downstream of the -10 element. Here we identify two high-affinity H-NS sites, H-NS I, located at the 3' end of the extended upstream footprint, and H-NS II, located at the 5' end of the extended downstream footprint. It is suggested that these high-affinity sites initiate the progressive formation of higher order complexes, allowing a range of H-NS-mediated regulatory effects at PhlyE. Finally, the identification of a SlyA binding site that overlaps the H-NS I site in PhlyE suggests a mechanism to explain how SlyA overproduction enhances hlyE expression by antagonizing the negative effects of H-NS.
* Corresponding author. Mailing address: The Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield S10 2TN, United Kingdom. Phone: 44 114 2224403. Fax: 44 114 2728697. E-mail: jeff.green{at}sheffield.ac.uk.
Journal of Bacteriology, March 2004, p. 1620-1628, Vol. 186, No. 6
0021-9193/04/$08.00+0 DOI: 10.1128/JB.186.6.1620-1628.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.
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Copyright © 2004 by the American Society for Microbiology. All rights reserved.