title: Regulation of Pseudomonas aeruginosa virulence factors by two novel RNA thermometers.
abstract: In a number of bacterial pathogens, the production of virulence factors is induced at 37 °C; this effect is often regulated by mRNA structures formed in the 5' untranslated region (UTR) that block translation initiation of genes at environmental temperatures. At 37 °C, the RNA structures become unstable and ribosomes gain access to their binding sites in the mRNAs. Pseudomonas aeruginosa is an important opportunistic pathogen and the expression of many of its virulence-associated traits is regulated by the quorum-sensing (QS) response, but the effect of temperature on virulence-factor expression is not well-understood. The aim of this work is the characterization of the molecular mechanism involved in thermoregulation of QS-dependent virulence-factor production. We demonstrate that traits that are dependent on the QS transcriptional regulator RhlR have a higher expression at 37 °C, correlating with a higher RhlR concentration as measured by Western blot. We also determined, using gene fusions and point mutations, that RhlR thermoregulation is a posttranscriptional effect dependent on an RNA thermometer of the ROSE (Repression Of heat-Shock gene Expression) family. This RNA element regulates the expression of the rhlAB operon, involved in rhamnolipid production, and of the downstream rhlR gene. We also identified a second functional thermometer in the 5' UTR of the lasI gene. We confirmed that these RNA thermometers are the main mechanism of thermoregulation of QS-dependent gene expression in P. aeruginosa using quantitative real-time PCR. This is the first description, to our knowledge, of a ROSE element regulating the expression of virulence traits and of an RNA thermometer controlling multiple genes in an operon through a polar effect.
authors.affiliation: Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Apdo. Postal 70228, Ciudad Universitaria, D.F. 04510, México;
authors.forename: María Victoria
authors.initials: MV
authors.lastname: Grosso-Becerra
authors.affiliation: Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Apdo. Postal 70228, Ciudad Universitaria, D.F. 04510, México;
authors.forename: Gerardo
authors.initials: G
authors.lastname: Croda-García
authors.affiliation: Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Mor. 62200, México; and.
authors.forename: Enrique
authors.initials: E
authors.lastname: Merino
authors.affiliation: Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Apdo. Postal 70228, Ciudad Universitaria, D.F. 04510, México;
authors.forename: Luis
authors.initials: L
authors.lastname: Servín-González
authors.affiliation: Unidad de Genotipificación y Análisis de Expresión, Instituto Nacional de Medicina Genómica, México, D.F. 14090, Secretaría de Salud, México.
authors.forename: Raúl
authors.initials: R
authors.lastname: Mojica-Espinosa
authors.affiliation: Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Apdo. Postal 70228, Ciudad Universitaria, D.F. 04510, México; gloria@biomedicas.unam.mx.
authors.forename: Gloria
authors.initials: G
authors.lastname: Soberón-Chávez
mesh_terms: D020121:5' Untranslated Regions / Q000235:genetics; D001426:Bacterial Proteins / Q000378:metabolism; D001483:Base Sequence; D015964:Gene Expression Regulation, Bacterial; D006714:Homoserine / Q000031:analogs & derivatives / Q000378:metabolism; D042541:Intracellular Space / Q000378:metabolism; D007783:Lactones / Q000378:metabolism; D008969:Molecular Sequence Data; D009876:Operon / Q000235:genetics; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity*; D012329:RNA, Bacterial / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D013696:Temperature; D014158:Transcription, Genetic; D037521:Virulence Factors / Q000378:metabolism*
chemical_list: D020121:5' Untranslated Regions; D001426:Bacterial Proteins; D007783:Lactones; D012329:RNA, Bacterial; C086515:RhlR protein, Pseudomonas aeruginosa; D037521:Virulence Factors; C085113:Pseudomonas aeruginosa autoinducer; D006714:Homoserine
keywords: RNA thermometers; bacterial virulence; gene regulation; polarity; quorum sensing