Regulatory control of the Escherichia coli O157:H7 lpf1 operon by H-NS and Ler

Maricarmen Rojas-López, Margarita M.P. Arenas-Hernández, Abraham Medrano-López, Claudia F. Martínez De La Peña, José Luis Puente, Ygnacio Martínez-Laguna, Alfredo G. Torres

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19 Scopus citations

Abstract

Long polar fimbriae 1 (Lpf1) of Escherichia coli O157:H7 is a tightly regulated adhesin, with H-NS silencing the transcriptional expression of the lpf1 operon while Ler (locus of enterocyte effacement-encoded regulator) acts as an antisilencer. We mapped the minimal regulatory region of lpf1 required for H-NS- and Ler-mediated regulation and found that it is 79% AT rich. Three putative sites for H-NS binding were identified. Two of them, named silencer regulatory sequence 1 (SRS1) and SRS2, are located on a region that covers both of the lpf1 promoters (P1 and P2). The third putative H-NS binding site is located within the lpfA1 gene in a region extending from +258 bp to +545 bp downstream of ATG; however, this site does not seem to play a role in lpfA1 regulation under the conditions tested in this work. Ler was also found to interact with Ler binding sites (LBSs). Ler binding site 1 (LBS1) and LBS2 are located upstream of the two promoters. LBS1 overlaps SRS1, while LBS3 overlaps the P1 promoter and SRS2. Based on the experimental data, we propose that H-NS silences lpf1 expression by binding to both of the SRSs on the promoter region, forming an SRS-H-NS complex that prevents RNA polymerase-mediated transcription. A model of the regulation of the lpfA1 operon of E. coli O157:H7 by H-NS and Ler is discussed.

Original languageEnglish (US)
Pages (from-to)1622-1632
Number of pages11
JournalJournal of bacteriology
Volume193
Issue number7
DOIs
StatePublished - Apr 2011

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology

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    Rojas-López, M., Arenas-Hernández, M. M. P., Medrano-López, A., Martínez De La Peña, C. F., Puente, J. L., Martínez-Laguna, Y., & Torres, A. G. (2011). Regulatory control of the Escherichia coli O157:H7 lpf1 operon by H-NS and Ler. Journal of bacteriology, 193(7), 1622-1632. https://doi.org/10.1128/JB.01082-10