Involvement of FIS in the H-NS-mediated regulation of virF gene of Shigella and enteroinvasive Escherichia coli

Citation
M. Falconi et al., Involvement of FIS in the H-NS-mediated regulation of virF gene of Shigella and enteroinvasive Escherichia coli, MOL MICROB, 42(2), 2001, pp. 439-452
Citations number
54
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Microbiology
Journal title
MOLECULAR MICROBIOLOGY
ISSN journal
0950-382X → ACNP
Volume
42
Issue
2
Year of publication
2001
Pages
439 - 452
Database
ISI
SICI code
0950-382X(200110)42:2<439:IOFITH>2.0.ZU;2-R
Abstract
The mechanism of pathogenicity in Shigella and enteroinvasive Escherichia c oli (EIEC) requires the co-ordinated expression of several genes located on both the virulence plasmid and the chromosome. We found that cells lacking a functional FIS protein (factor for inversion stimulation) are partially impaired in expressing the virulence genes and that full expression is tota lly restored when Shigella wildtype fis gene is offered in trans. We also i dentified virF, among the virulence genes, as a target of FIS-mediated acti vation and showed that FIS binds to four specific sites in the promoter reg ion of virF. Previous studies have demonstrated that the expression of VirF , the first positive activator of a multistep regulatory cascade, is subjec t to temperature-dependent regulation by H-NS, one of the main nucleoid-ass ociated proteins. We now demonstrate that two of the four FIS sites overlap one of the two H-NS sites responsible for thermoregulation (H-NS site I). FIS was found to exercise a direct positive transcriptional control at perm issive temperature (37 degreesC), when H-NS fails to repress virF, as well as an indirect effect by partially counteracting H-NS inhibition at the tra nsition temperature (32 degreesC). Our data indicate that FIS may be releva nt for the rapid increase in virF expression after penetration of bacteria into the host.