title: The AfaR small RNA controls expression of the AfaD-VIII invasin in pathogenic Escherichia coli strains.
abstract: Pathogenic Escherichia coli strains carrying the afa-8 gene cluster are frequently associated with extra-intestinal infections in humans and animals. The afa-8 A to E genes determine the formation of an afimbrial adhesive sheath consisting of the AfaD-VIII invasin and the AfaE-VIII adhesin at the bacterial cell surface. This structure is thought to be required for host colonization. We characterized a new gene encoding the small RNA AfaR, which is transcribed in cis from the complementary strand of the 3' untranslated region of the afaD messenger RNA, within the afaD-afaE intercistronic region. AfaR is a trans-acting Hfq-dependent antisense small RNA that binds the 5' untranslated region of the afaD messenger RNA, initiating several ribonuclease E-dependent cleavages, thereby downregulating production of the AfaD-VIII invasin. AfaR transcription is dependent on σ(E), a member of the stress response family of extracytoplasmic alternative sigma factors. We found that the AfaR-dependent regulatory pathway was controlled by temperature, allowing the production of the AfaD-VIII invasin at temperatures above 37 °C. Our findings suggest that the entry of afa-8-positive pathogenic E. coli strains into epithelial cells is tightly regulated by the AfaR small RNA.
authors.affiliation: Institut Pasteur, Unité de Biologie des Bactéries Pathogènes à Gram Positif, 25-28 Rue du Docteur Roux, F-75724 Paris, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Pichon
authors.forename: Laurence
authors.initials: L
authors.lastname: du Merle
authors.forename: Isabelle
authors.initials: I
authors.lastname: Lequeutre
authors.forename: Chantal
authors.initials: C
authors.lastname: Le Bouguénec
mesh_terms: D018830:Adhesins, Escherichia coli / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D004722:Endoribonucleases / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000502:physiology; D015964:Gene Expression Regulation, Bacterial; D035001:Host Factor 1 Protein / Q000502:physiology; D008969:Molecular Sequence Data; D005810:Multigene Family; D011401:Promoter Regions, Genetic; D020871:RNA Stability; D016372:RNA, Antisense / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D058727:RNA, Small Untranslated / Q000378:metabolism*; D012808:Sigma Factor / Q000378:metabolism; D013696:Temperature; D014158:Transcription, Genetic
chemical_list: D018830:Adhesins, Escherichia coli; C108510:AfaD protein, E coli; D029968:Escherichia coli Proteins; C087373:Hfq protein, E coli; D035001:Host Factor 1 Protein; D016372:RNA, Antisense; D012333:RNA, Messenger; D058727:RNA, Small Untranslated; D012808:Sigma Factor; C063202:sporulation-specific sigma factors; D004722:Endoribonucleases; C022537:ribonuclease E
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