Involvement of FIS in the H-NS-mediated regulation of virF gene of Shigella and enteroinvasive Escherichia coli.
The mechanism of pathogenicity in Shigella and enteroinvasive Escherichia coli (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 totally restored when Shigella wild-type fis gene is offered in trans. We also identified virF, among the virulence genes, as a target of FIS-mediated activation and showed that FIS binds to four specific sites in the promoter region of virF. Previous studies have demonstrated that the expression of VirF, the first positive activator of a multistep regulatory cascade, is subject to temperature-dependent regulation by H-NS, one of the main nucleoid-associated 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 permissive temperature (37 degrees C), when H-NS fails to repress virF, as well as an indirect effect by partially counteracting H-NS inhibition at the transition temperature (32 degrees C). Our data indicate that FIS may be relevant for the rapid increase in virF expression after penetration of bacteria into the host.
Falconi
M
M
Laboratorio di Genetica, Dipartimento di Biologia MCA, Università di Camerino, 62032 Camerino (MC), Italy.
Prosseda
G
G
Giangrossi
M
M
Beghetto
E
E
Colonna
B
B
D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D018983:DNA Footprinting; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics* / Q000472:pathogenicity*; D029968:Escherichia coli Proteins; D035021:Factor For Inversion Stimulation Protein; D015964:Gene Expression Regulation, Bacterial; D034982:Integration Host Factors; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D020218:Response Elements / Q000235:genetics; D012760:Shigella / Q000235:genetics* / Q000502:physiology; D013696:Temperature; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D014774:Virulence / Q000235:genetics; D037521:Virulence Factors
D001426:Bacterial Proteins; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D035021:Factor For Inversion Stimulation Protein; C031908:H-NS protein, bacteria; D034982:Integration Host Factors; D012097:Repressor Proteins; D014157:Transcription Factors; D037521:Virulence Factors; C440502:integration host factor, E coli