title: RfaH suppresses small RNA MicA inhibition of fimB expression in Escherichia coli K-12.
abstract: The phase variation (reversible on-off switching) of the type 1 fimbrial adhesin of Escherichia coli involves a DNA inversion catalyzed by FimB (switching in either direction) or FimE (on-to-off switching). Here, we demonstrate that RfaH activates expression of a FimB-LacZ protein fusion while having a modest inhibitory effect on a comparable fimB-lacZ operon construct and on a FimE-LacZ protein fusion, indicating that RfaH selectively controls fimB expression at the posttranscriptional level. Further work demonstrates that loss of RfaH enables small RNA (sRNA) MicA inhibition of fimB expression even in the absence of exogenous inducing stress. This effect is explained by induction of σ(E), and hence MicA, in the absence of RfaH. Additional work confirms that the procaine-dependent induction of micA requires OmpR, as reported previously (A. Coornaert et al., Mol. Microbiol. 76:467-479, 2010, doi:10.1111/j.1365-2958.2010.07115.x), but also demonstrates that RfaH inhibition of fimB transcription is enhanced by procaine independently of OmpR. While the effect of procaine on fimB transcription is shown to be independent of RcsB, it was found to require SlyA, another known regulator of fimB transcription. These results demonstrate a complex role for RfaH as a regulator of fimB expression.
authors.affiliation: School of Biosciences, University of Kent, Canterbury, Kent, United Kingdom.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Moores
authors.forename: Saranna
authors.initials: S
authors.lastname: Chipper-Keating
authors.forename: Lei
authors.initials: L
authors.lastname: Sun
authors.forename: Gareth
authors.initials: G
authors.lastname: McVicker
authors.forename: Lynn
authors.initials: L
authors.lastname: Wales
authors.forename: Krishna
authors.initials: K
authors.lastname: Gashi
authors.forename: Ian C
authors.initials: IC
authors.lastname: Blomfield
mesh_terms: D019677:Artificial Gene Fusion; D004268:DNA-Binding Proteins / Q000096:biosynthesis*; D048168:Escherichia coli K12 / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000096:biosynthesis* / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D019426:Integrases / Q000096:biosynthesis*; D010445:Peptide Elongation Factors / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism*; D001616:beta-Galactosidase / Q000032:analysis / Q000235:genetics
chemical_list: D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D010445:Peptide Elongation Factors; D034741:RNA, Small Interfering; C106401:RfaH protein, E coli; D015534:Trans-Activators; C081956:fimB protein, E coli; D019426:Integrases; D001616:beta-Galactosidase