title: Transcriptional control of the pvdS iron starvation sigma factor gene by the master regulator of sulfur metabolism CysB in Pseudomonas aeruginosa.
abstract: In the Gram-negative pathogen Pseudomonas aeruginosa, the alternative sigma factor PvdS acts as a key regulator of the response to iron starvation. PvdS also controls P. aeruginosa virulence, as it drives the expression of a large set of genes primarily implicated in biogenesis and transport of the pyoverdine siderophore and synthesis of extracellular factors, such as protease PrpL and exotoxin A. Besides the ferric uptake regulatory protein Fur, which shuts off pvdS transcription under iron-replete conditions, no additional regulatory factor(s) controlling the pvdS promoter activity have been characterized so far. Here, we used the promoter region of pvdS as bait to tentatively capture, by DNA-protein affinity purification, P. aeruginosa proteins that are able to bind specifically to the pvdS promoter. This led to the identification and functional characterization of the LysR-like transcription factor CysB as a novel regulator of pvdS transcription. The CysB protein directly binds to the pvdS promoter in vitro and acts as a positive regulator of PvdS expression in vivo. The absence of a functional CysB protein results in about 50% reduction of expression of PvdS-dependent virulence phenotypes. Given the role of CysB as master regulator of sulfur metabolism, our findings establish a novel molecular link between the iron and sulfur regulons in P. aeruginosa.
authors.affiliation: Department of Biology, University 'Roma Tre', Viale G. Marconi 446-00146 Rome, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Imperi
authors.forename: Federica
authors.initials: F
authors.lastname: Tiburzi
authors.forename: Gian Maria
authors.initials: GM
authors.lastname: Fimia
authors.forename: Paolo
authors.initials: P
authors.lastname: Visca
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D007501:Iron / Q000378:metabolism*; D009842:Oligopeptides / Q000378:metabolism; D011550:Pseudomonas aeruginosa / Q000235:genetics* / Q000378:metabolism* / Q000472:pathogenicity; D012808:Sigma Factor / Q000235:genetics* / Q000378:metabolism; D013455:Sulfur / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; C062886:CysB protein, Bacteria; C111692:MvaT protein, Pseudomonas; D009842:Oligopeptides; C093593:PvdS protein, Pseudomonas aeruginosa; D012808:Sigma Factor; D015534:Trans-Activators; D013455:Sulfur; C042453:pyoverdin; D007501:Iron