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Distant cis ‐active sequences and sialic acid control the expression of fimB in Escherichia coli K‐12
Author(s) -
ElLabany Sammia,
Sohanpal Baljinder K.,
Lahooti Maryam,
Akerman Robert,
Blomfield Ian C.
Publication year - 2003
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2003.03624.x
Subject(s) - biology , phase variation , genetics , operon , escherichia coli , gene , dna , recombinase , microbiology and biotechnology , recombination , phenotype
Summary 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.