Affiliation:
1. The Biodesign Institute
2. School of Life Sciences, Arizona State University, P.O. Box 875401, 1001 S. McAllister Ave., Tempe, Arizona 85287
Abstract
ABSTRACT
Leucine-responsive regulatory protein (Lrp) is a global gene regulator that influences expression of a large number of genes including virulence-related genes in
Escherichia coli
and
Salmonella
. No systematic studies examining the regulation of virulence genes by Lrp have been reported in
Salmonella
. We report here that constitutive expression of Lrp [
lrp
(Con)] dramatically attenuates
Salmonella
virulence while an
lrp
deletion (Δ
lrp
) mutation enhances virulence. The
lrp
(Con) mutant caused pleiotropic effects that include defects in invasion, cytotoxicity, and colonization, whereas the Δ
lrp
mutant was more proficient at these activities than the wild-type strain. We present evidence that Lrp represses transcription of key virulence regulator genes—
hilA
,
invF
, and
ssrA
—in
Salmonella
pathogenicity island 1 (SPI-1) and 2 (SPI-2), by binding directly to their promoter regions, P
hilA
, P
invF
, and P
ssrA
. In addition, Western blot analysis showed that the expression of the SPI-1 effector SipA was reduced in the
lrp
(Con) mutant and enhanced in the Δ
lrp
mutant. Computational analysis revealed putative Lrp-binding consensus DNA motifs located in P
hilA
, P
invF
, and P
ssrA
. These results suggest that Lrp binds to the consensus motifs and modulates expression of the linked genes. The presence of leucine enhanced Lrp binding to P
invF
in vitro and the addition of leucine to growth medium decreased the level of
invF
transcription. However, leucine had no effect on expression of
hilA
and
ssrA
or on cellular levels of Lrp. In addition, Lrp appears to be an antivirulence gene, since the deletion mutant showed enhanced cell invasion, cytotoxicity, and hypervirulence in BALB/c mice.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Reference98 articles.
1. Akbar, S., L. M. Schechter, C. P. Lostroh, and C. A. Lee. 2003. AraC/XylS family members, HilD and HilC, directly activate virulence gene expression independently of HilA in Salmonella typhimurium. Mol. Microbiol. 47 : 715-728.
2. Altier, C., M. Suyemoto, A. I. Ruiz, K. D. Burnham, and R. Maurer. 2000. Characterization of two novel regulatory genes affecting Salmonella invasion gene expression. Mol. Microbiol. 35 : 635-646.
3. Arricau, N., D. Hermant, H. Waxin, C. Ecobichon, P. S. Duffey, and M. Y. Popoff. 1998. The RcsB-RcsC regulatory system of Salmonella typhi differentially modulates the expression of invasion proteins, flagellin and Vi antigen in response to osmolarity. Mol. Microbiol. 29 : 835-850.
4. Baek, C.-H., and K.-S. Kim. 2003. lacZ- and aph-based reporter vectors for in vivo expression technology. J. Microbiol. Biotechnol. 13 : 872-880.
5. Baek, C.-H., K.-E. Lee, D.-K. Park, S.-H. Choi, and K.-S. Kim. 2007. Genetic analysis of spontaneous lactose-utilizing mutants from Vibrio vulnificus. J. Microbiol. Biotechnol. 17 : 2046-2055.
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