Binding site recognition by Rns, a virulence regulator in the AraC family

George Munson, June R. Scott

Research output: Contribution to journalArticle

44 Citations (Scopus)

Abstract

The expression of CS1 pili by enterotoxigenic strains of Escherichia coli is regulated at the transcriptional level and requires the virulence regulator Rns, a member of the AraC family of regulatory proteins. Rns binds at two separate sites upstream of Pcoo (the promoter of CS1 pilin genes), which were identified in vitro with an MBP::Rns fusion protein in gel mobility and DNase I footprinting assays. At each site, Rns recognizes asymmetric nucleotide sequences in two regions of the major groove and binds along one face of the DNA helix. Both binding sites are required for activation of Pcoo in vivo, because mutagenesis of either site significantly reduced the level of expression from this promoter. Thus, Rns regulates the expression of CS1 pilin genes directly, not via a regulatory cascade. Analysis of Rns-nucleotide interactions at each site suggests that binding sites for Rns and related virulence regulators are not easily identified because they do not bind palindromic or repeated sequences. A strategy to identify asymmetric binding sites is presented and applied to locate potential binding sites upstream of other genes that Rns can activate, including those encoding the CS2 and CFA/I pill of enterotoxigenic E. coli and the global regulator virB of Shigella flexneri.

Original languageEnglish
Pages (from-to)2110-2117
Number of pages8
JournalJournal of Bacteriology
Volume181
Issue number7
StatePublished - Apr 1 1999
Externally publishedYes

Fingerprint

Virulence
Binding Sites
Fimbriae Proteins
Enterotoxigenic Escherichia coli
Genes
Shigella flexneri
Deoxyribonuclease I
Mutagenesis
Proteins
Nucleotides
Gels
DNA

ASJC Scopus subject areas

  • Applied Microbiology and Biotechnology
  • Immunology

Cite this

Binding site recognition by Rns, a virulence regulator in the AraC family. / Munson, George; Scott, June R.

In: Journal of Bacteriology, Vol. 181, No. 7, 01.04.1999, p. 2110-2117.

Research output: Contribution to journalArticle

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AB - The expression of CS1 pili by enterotoxigenic strains of Escherichia coli is regulated at the transcriptional level and requires the virulence regulator Rns, a member of the AraC family of regulatory proteins. Rns binds at two separate sites upstream of Pcoo (the promoter of CS1 pilin genes), which were identified in vitro with an MBP::Rns fusion protein in gel mobility and DNase I footprinting assays. At each site, Rns recognizes asymmetric nucleotide sequences in two regions of the major groove and binds along one face of the DNA helix. Both binding sites are required for activation of Pcoo in vivo, because mutagenesis of either site significantly reduced the level of expression from this promoter. Thus, Rns regulates the expression of CS1 pilin genes directly, not via a regulatory cascade. Analysis of Rns-nucleotide interactions at each site suggests that binding sites for Rns and related virulence regulators are not easily identified because they do not bind palindromic or repeated sequences. A strategy to identify asymmetric binding sites is presented and applied to locate potential binding sites upstream of other genes that Rns can activate, including those encoding the CS2 and CFA/I pill of enterotoxigenic E. coli and the global regulator virB of Shigella flexneri.

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