title: Mechanism of hcnA mRNA recognition in the Gac/Rsm signal transduction pathway of Pseudomonas fluorescens.
abstract: In the plant-beneficial bacterium Pseudomonas fluorescens CHA0, the expression of antifungal exoproducts is controlled by the GacS/GacA two-component system. Two RNA binding proteins (RsmA, RsmE) ensure effective translational repression of exoproduct mRNAs. At high cell population densities, GacA induces three small RNAs (RsmX, RsmY, RsmZ) which sequester both RsmA and RsmE, thereby relieving translational repression. Here we systematically analyse the features that allow the RNA binding proteins to interact strongly with the 5' untranslated leader mRNA of the P. fluorescens hcnA gene (encoding hydrogen cyanide synthase subunit A). We obtained evidence for three major RsmA/RsmE recognition elements in the hcnA leader, based on directed mutagenesis, RsmE footprints and toeprints, and in vivo expression data. Two recognition elements were found in two stem-loop structures whose existence in the 5' leader region was confirmed by lead(II) cleavage analysis. The third recognition element, which overlapped the hcnA Shine-Dalgarno sequence, was postulated to adopt either an open conformation, which would favour ribosome binding, or a stem-loop structure, which may form upon interaction with RsmA/RsmE and would inhibit access of ribosomes. Effective control of hcnA expression by the Gac/Rsm system appears to result from the combination of the three appropriately spaced recognition elements.
authors.affiliation: Département de Microbiologie Fondamentale, Université de Lausanne, Bâtiment Biophore, CH-1015 Lausanne, Switzerland.
authors.forename: Karine
authors.initials: K
authors.lastname: Lapouge
authors.forename: Elena
authors.initials: E
authors.lastname: Sineva
authors.forename: Magnus
authors.initials: M
authors.lastname: Lindell
authors.forename: Katja
authors.initials: K
authors.lastname: Starke
authors.forename: Carol S
authors.initials: CS
authors.lastname: Baker
authors.forename: Paul
authors.initials: P
authors.lastname: Babitzke
authors.forename: Dieter
authors.initials: D
authors.lastname: Haas
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D024202:Electrophoretic Mobility Shift Assay; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D009154:Mutation; D050891:Oxidoreductases Acting on CH-NH2 Group Donors / Q000235:genetics* / Q000378:metabolism*; D011485:Protein Binding; D011551:Pseudomonas fluorescens / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; C091100:GacA protein, Bacteria; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D050891:Oxidoreductases Acting on CH-NH2 Group Donors; C112800:glycine dehydrogenase (cyanide-forming); D001616:beta-Galactosidase