title: SlyA protein activates fimB gene expression and type 1 fimbriation in Escherichia coli K-12.
abstract: We have demonstrated that SlyA activates fimB expression and hence type 1 fimbriation, a virulence factor in Escherichia coli. SlyA is shown to bind to two operator sites (O(SA1) and O(SA2)), situated between 194 and 167 base pairs upstream of the fimB transcriptional start site. fimB expression is derepressed in an hns mutant and diminished by a slyA mutation in the presence of H-NS only. H-NS binds to multiple sites in the promoter region, including two sites (H-NS2 and H-NS3) that overlap O(SA1) and O(SA2), respectively. Mutations that disrupt either O(SA1) or O(SA2) eliminate or reduce the activating effect of SlyA but have different effects on the level of expression. We interpret these results as reflecting the relative competition between SlyA and H-NS binding. Moreover we show that SlyA is capable of displacing H-NS from its binding sites in vitro. We suggest SlyA binding prevents H-NS binding to H-NS2 and H-NS3 and the subsequent oligomerization of H-NS necessary for full inhibition of fimB expression. In addition, we show that SlyA activates fimB expression independently of two other known regulators of fimB expression, NanR and NagC. It is demonstrated that the rarely used UUG initiation codon limits slyA expression and that low SlyA levels limit fimB expression. Furthermore, Western blot analysis shows that cells grown in rich-defined medium contain ~1000 SlyA dimers per cell whereas those grown in minimal medium contain >20% more SlyA. This study extends our understanding of the role that SlyA plays in the host-bacterial relationship.
authors.affiliation: School of Biosciences, University of Kent, Canterbury CT2 7NJ, United Kingdom.
authors.forename: Gareth
authors.initials: G
authors.lastname: McVicker
authors.forename: Lei
authors.initials: L
authors.lastname: Sun
authors.forename: Baljinder K
authors.initials: BK
authors.lastname: Sohanpal
authors.forename: Krishna
authors.initials: K
authors.lastname: Gashi
authors.forename: Richard A
authors.initials: RA
authors.lastname: Williamson
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Plumbridge
authors.forename: Ian C
authors.initials: IC
authors.lastname: Blomfield
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D048168:Escherichia coli K12 / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D029968:Escherichia coli Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D036781:Fimbriae Proteins / Q000235:genetics / Q000378:metabolism; D010861:Fimbriae, Bacterial / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D054884:Host-Pathogen Interactions / Q000235:genetics; D019426:Integrases / Q000096:biosynthesis* / Q000235:genetics; D009154:Mutation; D009875:Operator Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D037521:Virulence Factors / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C529458:FimG protein, E coli; C477082:NanR protein, E coli; D012097:Repressor Proteins; D014157:Transcription Factors; D037521:Virulence Factors; C081956:fimB protein, E coli; C067862:nagC protein, E coli; C056785:salmolysin; D036781:Fimbriae Proteins; D019426:Integrases