title: Integration Host Factor is required for FarR repression of the farAB-encoded efflux pump of Neisseria gonorrhoeae.
abstract: The farAB operon encodes an efflux pump system that mediates the resistance of Neisseria gonorrhoeae to antimicrobial long-chain fatty acids. We previously observed that expression of farAB is negatively regulated by the FarR repressor. In this study, we examined the molecular mechanism by which FarR represses expression of farAB. DNase I footprinting analysis, coupled with a deletion analysis of the farAB promoter region, indicated that FarR binds to three sites (termed sites A, B and C) within the DNA sequence upstream of farA; genetic analysis revealed, however, that site B is not required for FarR repression of farAB. This repression also required the presence of Integration Host Factor (IHF), which was found to bind to sequences located between FarR binding sites A and C. We determined that IHF binding to the farAB promoter region could inhibit transcription in vitro and that such binding induced a bending of the target DNA, which we propose to be important in regulating this operon. IHF binding to the promoter region was found to stabilize the binding of FarR to its binding sites A and C and as a consequence, enhanced repression of farAB expression mediated by FarR. We propose a model in which expression of the farAB-encoded efflux pump in N. gonorrhoeae is modulated by the DNA binding activities of FarR and IHF.
authors.affiliation: Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, GA 30322, USA.
authors.forename: Eun-Hee
authors.initials: EH
authors.lastname: Lee
authors.forename: Stuart A
authors.initials: SA
authors.lastname: Hill
authors.forename: Ruth
authors.initials: R
authors.lastname: Napier
authors.forename: William M
authors.initials: WM
authors.lastname: Shafer
mesh_terms: D020029:Base Pairing; D001665:Binding Sites / Q000235:genetics; D004269:DNA, Bacterial / Q000737:chemistry / Q000378:metabolism; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D005227:Fatty Acids / Q000378:metabolism / Q000494:pharmacology; D015964:Gene Expression Regulation, Bacterial; D034982:Integration Host Factors / Q000378:metabolism*; D008969:Molecular Sequence Data; D009344:Neisseria gonorrhoeae / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D009876:Operon / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics; D023302:Protein Footprinting; D012097:Repressor Proteins / Q000378:metabolism*; D017384:Sequence Deletion
chemical_list: D004269:DNA, Bacterial; D005227:Fatty Acids; D034982:Integration Host Factors; D012097:Repressor Proteins