POSTERS - BLAST X - University of Utah
POSTERS - BLAST X - University of Utah
POSTERS - BLAST X - University of Utah
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<strong>BLAST</strong> X Poster #9<br />
THE LeuO REGULON IN SALMONELLA<br />
Edmundo Calva, Víctor H. Bustamante, Miguel Ángel De la Cruz, Marcos Fernández-Mora,<br />
Mario Alberto Flores-Valdez, Ana Lucía Gallego-Hernández, Carmen Guadarrama, Ismael<br />
Hernández-Lucas, Omar Ortega, Alejandra Vázquez, and Ricardo Oropeza.<br />
Instituto de Biotecnología UNAM, Cuernavaca, Morelos, Mexico.<br />
LeuO is a LysR-type transcriptional regulator, which antagonizes the repressing effect by<br />
the H-NS and StpA nucleoid proteins on the Salmonella enterica serovar Typhi ompS1<br />
quiescent porin gene, allowing the transcriptional activation by OmpR among other regulators.<br />
LeuO is also a positive regulator for the OmpS2 quiescent porin, for a quiescent putative<br />
periplasmic arylsulfate sulfotransferasa (AssT), and for an open reading frame <strong>of</strong> unknown<br />
function, STY3068. It is a negative regulator for the OmpX porin, a thiol peroxidase (Tpx), and<br />
for STY1978. These proteins were identified by a whole-genome proteomic analysis and the<br />
regulatory effects were confirmed on transcriptional gene reporter fusions. STY 3068 appears to<br />
be part <strong>of</strong> an operon (5’-STY3070-STY3064-3’), as transcriptional regulation occurs upstream,<br />
at STY 3070. The assT gene forms a LeuO-dependent operon with STY3371 and STY3372,<br />
which are paralogues <strong>of</strong> the dsbA and dsbB genes, respectively. This operon (5’-assT-<br />
STY3371-STY3372-3’) is repressed by OmpR.<br />
H-NS represses the expression <strong>of</strong> ompS1, assT and STY3070 and, on the other hand,<br />
activates the expression <strong>of</strong> tpx and STY1978. Expression <strong>of</strong> ompX was independent <strong>of</strong> H-NS.<br />
Interestingly, ompS2 is negatively regulated by H-NS in Escherichia coli and in S. Typhimurium,<br />
although in S. Typhi other negative regulators are involved aside from H-NS. LeuO specifically<br />
binds to the 5´ intergenic regions <strong>of</strong> ompS1, ompS2, assT, STY3070, ompX, and tpx. LeuO did<br />
not bind to the promoter region <strong>of</strong> STY1978, suggesting that it is regulating in an indirect<br />
manner.<br />
Hence, LeuO regulates a cadre <strong>of</strong> genes which appear to be mostly involved in the<br />
response to stress and in virulence.<br />
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