Dual function of the McaS small RNA in controlling biofilm formation: Genes Dev

Mikkel Girke Jørgensen, Maureen K. Thomason, Johannes Havelund, P. Valentin-Hansen, G. Storz

Research output: Contribution to journalJournal articleResearchpeer-review


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 beta-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.
Original languageEnglish
JournalGenes & Development
Pages (from-to)1132-1145
Publication statusPublished - 2013


  • Acetylglucosamine/biosynthesis Bacterial Outer Membrane Proteins/biosynthesis/genetics Base Pairing Biofilms/*growth & development Escherichia coli/*genetics/*growth & development Escherichia coli Proteins/biosynthesis/genetics/metabolism *Gene Expression Regulation, Bacterial/genetics Genes, Bacterial/genetics Host Factor 1 Protein/metabolism Phosphorus-Oxygen Lyases/biosynthesis/genetics Polysaccharides, Bacterial/biosynthesis Protein Biosynthesis RNA, Bacterial/*genetics/*metabolism RNA, Messenger/genetics/metabolism RNA, Untranslated/genetics/metabolism RNA-Binding Proteins/metabolism Regulon/genetics Repressor Proteins/metabolism
  • CsrB
  • Hfq
  • c-di-GMP
  • PGA
  • CsrA


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