title: HilA-like regulators in Escherichia coli pathotypes: the YgeH protein from the enteroaggregative strain 042.
abstract: BACKGROUND
  The HilA protein is the master regulator of the Salmonella pathogenicity island 1 (SPI1). EilA and YgeH proteins show a moderate similarity to HilA and are encoded in pathogenicity islands from several E. coli strains, both pathogenic and non-pathogenic. In the present work we characterize the YgeH protein from the enteroaggregative E. coli strain 042 (locus tag EC042_3050).
  
  
  RESULTS
  We show that both E. coli 042 YgeH and EilA proteins are able to functionally replace HilA in Salmonella. Interestingly, this is not the rule for all YgeH proteins: the YgeH protein from the enterohaemorragic E. coli strain O157 appears to be non-functional. ygeH expression is not influenced by growth osmolarity or temperature, and moderately increases in cells entering the stationary phase. H-NS represses ygeH expression under all growth conditions tested, and binds with specificity to the ygeH promoter region. As expected, expression of ETT2 (Escherichia coli type 3 secretion system 2) genes requires YgeH: ETT2 operons are downregulated in a ygeH mutant. Accordingly, since H-NS represses ygeH expression, ETT2 expression is significantly increased in an hns mutant.
  
  
  CONCLUSIONS
  E. coli 042 YgeH protein is functional and able to replace HilA in Salmonella. ETT2 gene expression requires YgeH activity which, in turn, is subjected to H-NS silencing.
authors.forename: Mário
authors.initials: M
authors.lastname: Hüttener
authors.forename: Manuela
authors.initials: M
authors.lastname: Dietrich
authors.forename: Sònia
authors.initials: S
authors.lastname: Paytubi
authors.affiliation: Institute for Bioengineering of Catalonia (IBEC), Barcelona, Spain. ajuarez@ub.edu.
authors.forename: Antonio
authors.initials: A
authors.lastname: Juárez
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D004269:DNA, Bacterial / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism*; D036781:Fimbriae Proteins / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D005816:Genetic Complementation Test; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; C513921:EilA protein, E coli; D029968:Escherichia coli Proteins; C529458:FimG protein, E coli; C102236:HilA protein, Salmonella; D015534:Trans-Activators; D014157:Transcription Factors; C000598494:YgeH protein, E coli; D036781:Fimbriae Proteins