Affiliation:
1. Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México
2. Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia, Canada
Abstract
ABSTRACT
The formation of attaching and effacing (A/E) lesions on intestinal epithelial cells is an essential step in the pathogenesis of human enteropathogenic and enterohemorrhagic
Escherichia coli
and of the mouse pathogen
Citrobacter rodentium
. The genes required for the development of the A/E phenotype are located within a pathogenicity island known as the
l
ocus of
e
nterocyte
e
ffacement (LEE). The LEE-encoded transcriptional regulators Ler, an H-NS-like protein, and GrlA, a member of a novel family of transcriptional activators, positively control the expression of the genes located in the LEE and their corresponding virulence. In this study, we used
C. rodentium
as a model to study the mechanisms controlling the expression of Ler and GrlA. By deletion analysis of the
ler
and
grlRA
regulatory regions and complementation experiments, negative and positive
cis
-acting regulatory motifs were identified that are essential for the regulation of both genes. This analysis confirmed that GrlA is required for the activation of
ler
, but it also showed that Ler is required for the expression of
grlRA
, revealing a novel regulatory loop controlling the optimal expression of virulence genes in A/E pathogens. Furthermore, our results indicate that Ler and GrlA induce the expression of each other by, at least in part, counteracting the repression mediated by H-NS. However, whereas GrlA is still required for the optimal expression of
ler
even in the absence of H-NS, Ler is not needed for the expression of
grlRA
in the absence of H-NS. This type of transcriptional positive regulatory loop represents a novel mechanism in pathogenic bacteria that is likely required to maintain an appropriate spatiotemporal transcriptional response during infection.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Reference49 articles.
1. Ausubel F. M. R. Brent R. E. Kingston D. D. Moore J. G. Seidman J. A. Smith and K. Struhl. 1989. Current protocols in molecular biology. John Wiley and Sons New York N.Y.
2. Ler Is a Negative Autoregulator of the
LEE1
Operon in Enteropathogenic
Escherichia coli
3. Buchet, A., W. Nasser, K. Eichler, and M. A. Mandrand-Berthelot. 1999. Positive co-regulation of the Escherichia coli carnitine pathway cai and fix operons by CRP and the CaiF activator. Mol. Microbiol.34:562-575.
4. Bustamante V. H. J. A. Ibarra K. Carrillo A. Vazquez and J. L. Puente. 2004. The locus of enterocyte effacement-encoded regulator (Ler) overcomes repression of type III secretion operons by modifying a nucleoprotein complex formed by H-NS. Presented at the 104th General Meeting of the American Society for Microbiology New Orleans La. 23 to 27 May 2004.
5. Bustamante, V. H., F. J. Santana, E. Calva, and J. L. Puente. 2001. Transcriptional regulation of type III secretion genes in enteropathogenic Escherichia coli: Ler antagonizes H-NS-dependent repression. Mol. Microbiol.39:664-678.
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