title: An unusual CsrA family member operates in series with RsmA to amplify posttranscriptional responses in Pseudomonas aeruginosa.
abstract: Members of the CsrA family of prokaryotic mRNA-binding proteins alter the translation and/or stability of transcripts needed for numerous global physiological processes. The previously described CsrA family member in Pseudomonas aeruginosa (RsmA) plays a central role in determining infection modality by reciprocally regulating processes associated with acute (type III secretion and motility) and chronic (type VI secretion and biofilm formation) infection. Here we describe a second, structurally distinct RsmA homolog in P. aeruginosa (RsmF) that has an overlapping yet unique regulatory role. RsmF deviates from the canonical 5 β-strand and carboxyl-terminal α-helix topology of all other CsrA proteins by having the α-helix internally positioned. Despite striking changes in topology, RsmF adopts a tertiary structure similar to other CsrA family members and binds a subset of RsmA mRNA targets, suggesting that RsmF activity is mediated through a conserved mechanism of RNA recognition. Whereas deletion of rsmF alone had little effect on RsmA-regulated processes, strains lacking both rsmA and rsmF exhibited enhanced RsmA phenotypes for markers of both type III and type VI secretion systems. In addition, simultaneous deletion of rsmA and rsmF resulted in superior biofilm formation relative to the wild-type or rsmA strains. We show that RsmF translation is derepressed in an rsmA mutant and demonstrate that RsmA specifically binds to rsmF mRNA in vitro, creating a global hierarchical regulatory cascade that operates at the posttranscriptional level.
authors: Cystic Fibrosis/Pulmonary Research and Treatment Center and Departments of Chemistry, Biochemistry and Biophysics, and Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599.
authors: Jeremiah N
authors: JN
authors: Marden
authors: Manisha R
authors: MR
authors: Diaz
authors: William G
authors: WG
authors: Walton
authors: Cindy J
authors: CJ
authors: Gode
authors: Laurie
authors: L
authors: Betts
authors: Mark L
authors: ML
authors: Urbanowski
authors: Matthew R
authors: MR
authors: Redinbo
authors: Timothy L
authors: TL
authors: Yahr
authors: Matthew C
authors: MC
authors: Wolfgang
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D018441:Biofilms / Q000254:growth & development; D005798:Genes, Bacterial; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D017434:Protein Structure, Tertiary; D011550:Pseudomonas aeruginosa / Q000235:genetics* / Q000378:metabolism*; D012323:RNA Processing, Post-Transcriptional; D012329:RNA, Bacterial / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018085:Regulon; D017386:Sequence Homology, Amino Acid
chemical_list: D001426:Bacterial Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; D016601:RNA-Binding Proteins
keywords: RsmY; RsmZ; signal transduction; virulence
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