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Infection and Immunity, January 2001, p. 186-193, Vol. 69, No. 1
Department of Microbiology and Immunology,
Emory University School of Medicine, Atlanta, Georgia 30322
Received 3 August 2000/Returned for modification 21 September
2000/Accepted 2 October 2000
Several regulators within the AraC family control the expression of
genes known or thought to be required for virulence of bacterial
pathogens. One of these, Rns, activates transcription from an
unprecedented variety of binding-site locations. Although nearly all
prokaryotic activators bind within a small region upstream and adjacent
to the promoter that they regulate, Rns does not bind within this
region to activate its own promoter, Prns. Instead, to
activate Prns, Rns requires one binding site 224.5 bp
upstream and one downstream of the transcription start site. We show in this study that several other AraC family activators recognize the same
binding sites as Rns and share with it the ability to utilize a
downstream binding site. Like Rns, other members of this group of
activators positively regulate the expression of virulence factors in
pathogenic bacteria. These regulators are also able to activate
transcription from promoter-proximal upstream binding sites since they
are able to substitute for Rns at Pcoo, a promoter with
only upstream binding sites. Thus, Rns is the prototype for a group of
regulators, which include CfaR, VirF, AggR, and CsvR and which activate
transcription from locations that are more diverse than those of any
other known activator.
0019-9567/01/$04.00+0 DOI: 10.1128/IAI.69.1.186-193.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Novel Group of Virulence Activators within the AraC
Family That Are Not Restricted to Upstream Binding Sites
*
Corresponding author. Mailing address: Department of
Microbiology and Immunology, Emory University School of Medicine,
Atlanta, GA 30322. Phone: (404) 727-0402. Fax: (404) 727-8999. E-mail: Scott{at}microbio.emory.edu.
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