title: PerC and GrlA independently regulate Ler expression in enteropathogenic Escherichia coli.
abstract: Ler, encoded by the locus of enterocyte effacement (LEE) of attaching and effacing (A/E) pathogens, induces the expression of LEE genes by counteracting the silencing exerted by H-NS. Ler expression is modulated by several global regulators, and is activated by GrlA, which is also LEE-encoded. Typical enteropathogenic Escherichia coli (EPEC) strains contain the EAF plasmid, which carries the perABC locus encoding PerC. The precise role of PerC in EPEC virulence gene regulation has remained unclear, mainly because EPEC strains lacking the pEAF still express the LEE genes and because PerC is not present in other A/E pathogens such as Citrobacter rodentium. Here, we describe that either PerC or GrlA can independently activate ler expression and, in consequence, of LEE genes depending on the growth conditions. Both PerC and GrlA, with the aid of IHF, counteract the repression exerted by H-NS on ler and can also further increase its activity. Our results substantiate the role of PerC and GrlA in EPEC virulence gene regulation and suggest that these convergent regulatory mechanisms may have represented an evolutionary adaptation in EPEC to co-ordinate the expression of plasmid- and chromosome-encoded virulence factors needed to successfully colonize its intestinal niche.
authors: Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, México.
authors: Víctor H
authors: VH
authors: Bustamante
authors: Miryam I
authors: MI
authors: Villalba
authors: Víctor A
authors: VA
authors: García-Angulo
authors: Alejandra
authors: A
authors: Vázquez
authors: Luary C
authors: LC
authors: Martínez
authors: Rafael
authors: R
authors: Jiménez
authors: José L
authors: JL
authors: Puente
mesh_terms: D001483:Base Sequence; D054308:Enteropathogenic Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; C513430:GrlA protein, E coli; C465556:Ler protein, E coli; C569462:PerC protein, E coli; D015534:Trans-Activators