title: Effects of local transcription and H-NS on inversion of the fim switch of Escherichia coli.
abstract: The fim switch of Escherichia coli is responsible for phase-variable expression of type 1 fimbriae. Switching in the ON-to-OFF and OFF-to-ON directions is promoted by the FimB recombinase, while the FimE recombinase directs switching predominantly in the ON-to-OFF direction. The effects of local promoter activity and the H-NS nucleoid-associated protein on inversion of the switch were assessed. In contrast to FimB-mediated inversion, inversion of the switch by the FimE recombinase was unaffected by the H-NS status of the cell. Transcription towards the switch from within a translationally inactivated fimE gene was found to bias the switch strongly in the OFF direction, creating a FimE+-like phenotype in the absence of the FimE protein. This biasing was H-NS dependent and was also contingent on transcription from within the switch. These data show that local transcription and a nucleoid-associated protein both contribute to the modulation of a site-specific recombination event on the bacterial chromosome.
authors.affiliation: Department of Microbiology, Moyne Institute of Preventive Medicine, University of Dublin, Trinity College, Dublin 2, Republic of Ireland.
authors.forename: J P
authors.initials: JP
authors.lastname: O'Gara
authors.forename: C J
authors.initials: CJ
authors.lastname: Dorman
mesh_terms: D000483:Alleles; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029968:Escherichia coli Proteins; D010861:Fimbriae, Bacterial / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D019426:Integrases / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011401:Promoter Regions, Genetic / Q000235:genetics; D011995:Recombination, Genetic; D012097:Repressor Proteins; D017422:Sequence Analysis, DNA; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C031908:H-NS protein, bacteria; D012097:Repressor Proteins; C081956:fimB protein, E coli; C081955:fimE protein, E coli; D019426:Integrases