title: Distant cis-active sequences and sialic acid control the expression of fimB in Escherichia coli K-12.
abstract: The phase variation of type 1 fimbriation in Escherichia coli is controlled by the inversion of a 314 bp element of DNA, determined by FimB (switching in both directions) or FimE (switching from the ON-to-OFF orientation predominantly), and influenced by auxiliary factors IHF, Lrp and H-NS. The fimB gene is separated from the divergently transcribed yjhATS operon by a large (1.4 kbp) intergenic region of unknown function. Here, we show that fimB expression is regulated by multiple cis-active sequences that lie far upstream (>600 bp) of the transcription start sites for the recombinase gene. Two regions characterized further (regions 1 and 2) show sequence identity, and each coincides with a methylation-protected Dam (5'-GATC) site. Regions 1 and 2 apparently control fimB expression by an antirepression mechanism that involves additional sequences proximal to yjhA. Region 1 encompasses a 27 bp DNA sequence conserved upstream of genes known (nanAT ) or suspected (yjhBC) to be involved in sialic acid metabolism, and we show that FimB expression and recombination are suppressed by N-acetylneuraminic acid. We propose that E. coli recognizes the amino sugars as a harbinger of potential host defence activation, and suppresses the expression of type 1 fimbriae in response.
authors.affiliation: Research School of Biosciences, University of Kent, Kent CT2 7NJ, UK.
authors.forename: Sammia
authors.initials: S
authors.lastname: El-Labany
authors.forename: Baljinder K
authors.initials: BK
authors.lastname: Sohanpal
authors.forename: Maryam
authors.initials: M
authors.lastname: Lahooti
authors.forename: Robert
authors.initials: R
authors.lastname: Akerman
authors.forename: Ian C
authors.initials: IC
authors.lastname: Blomfield
mesh_terms: D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics* / Q000502:physiology; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D019426:Integrases / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D011995:Recombination, Genetic; D012045:Regulatory Sequences, Nucleic Acid; D012794:Sialic Acids / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D012794:Sialic Acids; C081956:fimB protein, E coli; D019426:Integrases