title: Transcriptional regulation of Pseudomonas aeruginosa rhlR: role of the CRP orthologue Vfr (virulence factor regulator) and quorum-sensing regulators LasR and RhlR.
abstract: The production of many virulence factors by Pseudomonas aeruginosa is regulated by the quorum-sensing (QS) response. In this regulatory network LasR and RhlR, bound to their corresponding autoinducers, play a central role. The QS response has a hierarchical structure: LasR/3O-C12-HSL activates the transcription of rhlR, and RhlR/C4-HSL activates the transcription of several genes, including the rhlAB operon, which encodes the enzymes responsible for rhamnolipid synthesis. The rhlAB operon is located immediately upstream of the rhlR gene. rhlR has four transcription start sites, two of which are located in the rhlB coding region. Vfr directly activates transcription of lasR, and has been reported to be also involved in rhlR expression. The aim of this work was to characterize the details of the mechanism of rhlR transcriptional regulation. We show that Vfr directly regulates rhlR transcription through its binding to several Vfr-binding sites (VBSs) present in the rhlR promoter region, one of which has a negative effect on transcription. Two of the VBSs overlap with las boxes where LasR/3O-C12-HSL binds to activate rhlR transcription. We also show that rhlR transcription is subject to positive-feedback autoregulation through RhlR/C4-HSL activation of the rhlA promoter. This positive autoregulation plays a major role in rhlR expression.
authors: Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Apdo Postal 70228, México DF 04510, Mexico.
authors: Gerardo
authors: G
authors: Croda-García
authors: Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Apdo Postal 70228, México DF 04510, Mexico.
authors: Victoria
authors: V
authors: Grosso-Becerra
authors: Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Apdo Postal 70228, México DF 04510, Mexico.
authors: Abigail
authors: A
authors: Gonzalez-Valdez
authors: Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Apdo Postal 70228, México DF 04510, Mexico.
authors: Luis
authors: L
authors: Servín-González
authors: Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Apdo Postal 70228, México DF 04510, Mexico.
authors: Gloria
authors: G
authors: Soberón-Chávez
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D002373:Cyclic AMP Receptor Protein / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D006706:Homeostasis / Q000235:genetics; D008954:Models, Biological; D008969:Molecular Sequence Data; D059372:Nucleotide Motifs; D011401:Promoter Regions, Genetic; D011550:Pseudomonas aeruginosa / Q000235:genetics* / Q000378:metabolism; D053038:Quorum Sensing; D015534:Trans-Activators / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation
chemical_list: D001426:Bacterial Proteins; D002373:Cyclic AMP Receptor Protein; C080365:LasR protein, Pseudomonas aeruginosa; C086515:RhlR protein, Pseudomonas aeruginosa; D015534:Trans-Activators; C091090:Vfr protein, Pseudomonas aeruginosa