title: Dual function of the McaS small RNA in controlling biofilm formation.
abstract: Many bacterial small RNAs (sRNAs) regulate gene expression through base-pairing with mRNAs, and it has been assumed that these sRNAs act solely by this one mechanism. Here we report that the multicellular adhesive (McaS) sRNA of Escherichia coli uniquely acts by two different mechanisms: base-pairing and protein titration. Previous work established that McaS base pairs with the mRNAs encoding master transcription regulators of curli and flagella synthesis, respectively, resulting in down-regulation and up-regulation of these important cell surface structures. In this study, we demonstrate that McaS activates synthesis of the exopolysaccharide β-1,6 N-acetyl-D-glucosamine (PGA) by binding the global RNA-binding protein CsrA, a negative regulator of pgaA translation. The McaS RNA bears at least two CsrA-binding sequences, and inactivation of these sites compromises CsrA binding, PGA regulation, and biofilm formation. Moreover, ectopic McaS expression leads to induction of two additional CsrA-repressed genes encoding diguanylate cyclases. Collectively, our study shows that McaS is a dual-function sRNA with roles in the two major post-transcriptional regulons controlled by the RNA-binding proteins Hfq and CsrA.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense, Denmark;
authors.forename: Mikkel Girke
authors.initials: MG
authors.lastname: Jørgensen
authors.forename: Maureen K
authors.initials: MK
authors.lastname: Thomason
authors.forename: Johannes
authors.initials: J
authors.lastname: Havelund
authors.forename: Poul
authors.initials: P
authors.lastname: Valentin-Hansen
authors.forename: Gisela
authors.initials: G
authors.lastname: Storz
mesh_terms: D000117:Acetylglucosamine / Q000096:biosynthesis; D001425:Bacterial Outer Membrane Proteins / Q000096:biosynthesis / Q000235:genetics; D020029:Base Pairing; D018441:Biofilms / Q000254:growth & development*; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development*; D029968:Escherichia coli Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics; D005798:Genes, Bacterial / Q000235:genetics; D035001:Host Factor 1 Protein / Q000378:metabolism; D019761:Phosphorus-Oxygen Lyases / Q000096:biosynthesis / Q000235:genetics; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis; D014176:Protein Biosynthesis; D012329:RNA, Bacterial / Q000235:genetics* / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D022661:RNA, Untranslated / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism; D018085:Regulon / Q000235:genetics; D012097:Repressor Proteins / Q000378:metabolism
chemical_list: D001425:Bacterial Outer Membrane Proteins; C093587:CsrA protein, E coli; D029968:Escherichia coli Proteins; C087373:Hfq protein, E coli; D035001:Host Factor 1 Protein; D011135:Polysaccharides, Bacterial; D012329:RNA, Bacterial; D012333:RNA, Messenger; D022661:RNA, Untranslated; D016601:RNA-Binding Proteins; D012097:Repressor Proteins; C582298:pgaA protein, E coli; D019761:Phosphorus-Oxygen Lyases; C060720:diguanylate cyclase; D000117:Acetylglucosamine
keywords: CsrA; CsrB; Hfq; PGA; c-di-GMP