title: Characterization of BreR interaction with the bile response promoters breAB and breR in Vibrio cholerae.
abstract: The Vibrio cholerae BreR protein is a transcriptional repressor of the breAB efflux system operon, which encodes proteins involved in bile resistance. In a previous study (F. A. Cerda-Maira, C. S. Ringelberg, and R. K. Taylor, J. Bacteriol. 190:7441-7452, 2008), we used gel mobility shift assays to determine that BreR binds at two independent binding sites at the breAB promoter and a single site at its own promoter. Here it is shown, by DNase I footprinting and site-directed mutagenesis, that BreR is able to bind at a distal and a proximal site in the breAB promoter. However, only one of these sites, the proximal 29-bp site, is necessary for BreR-mediated transcriptional repression of breAB expression. In addition, it was determined that BreR represses its own expression by recognizing a 28-bp site at the breR promoter. These sites comprise regions of dyad symmetry within which residues critical for BreR function could be identified. The BreR consensus sequence AANGTANAC-N(6)-GTNTACNTT overlaps the -35 region at both promoters, implying that the repression of gene expression is achieved by interfering with RNA polymerase binding at these promoters.
authors.affiliation: Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, NH, USA.
authors.forename: Francisca A
authors.initials: FA
authors.lastname: Cerda-Maira
authors.forename: Gabriela
authors.initials: G
authors.lastname: Kovacikova
authors.forename: Brooke A
authors.initials: BA
authors.lastname: Jude
authors.forename: Karen
authors.initials: K
authors.lastname: Skorupski
authors.forename: Ronald K
authors.initials: RK
authors.lastname: Taylor
mesh_terms: D001646:Bile / Q000378:metabolism*; D018983:DNA Footprinting; D004269:DNA, Bacterial / Q000378:metabolism*; D003850:Deoxyribonuclease I / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D016297:Mutagenesis, Site-Directed; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012097:Repressor Proteins / Q000378:metabolism*; D014734:Vibrio cholerae / Q000187:drug effects / Q000235:genetics*
chemical_list: D004269:DNA, Bacterial; D012097:Repressor Proteins; D003850:Deoxyribonuclease I