title: Mycobacterium tuberculosis Rv1395 is a class III transcriptional regulator of the AraC family involved in cytochrome P450 regulation.
abstract: Rv1395 is annotated as a potential transcriptional regulator of the AraC family. The Rv1395 insertional mutant was identified in a signature tag mutagenesis study in Mycobacterium tuberculosis and was shown to be attenuated in the lungs of mice. Here, we used comparative genomics and biochemical methods to show that Rv1395 is unique to the M. tuberculosis complex and that it encodes a protein that binds the region between two divergent genes, a member of the cytochrome P450 family (Rv1394c or cyp132) and Rv1395 itself. Rv1395 binds to this DNA region by its helix-turn-helix-containing C-terminal domain, and it recognizes two sites with different affinity. We identified the transcriptional start points (TSP) of Rv1394c and Rv1395: both genes have two TSPs, three of which are located in the intergenic region. We constructed and compared various transcriptional fusions consisting of the promoter regions and a reporter gene in Mycobacterium smegmatis: this showed that Rv1395 induces the expression of the cytochrome P450 gene (Rv1394c) and represses its own transcription. This was confirmed in M. tuberculosis when the wild type and a Rv1395-overexpressing strain were used as hosts for the fusions. Site-directed mutagenesis showed that Rv1395 binds to the two sites in a co-operative manner and that binding to both sites is required for Rv1395 optimal activity. A model describing the potential mode of action of Rv1395 is discussed.
authors.affiliation: Unité de Génétique Mycobactérienne, Institut Pasteur, 25, Rue du Dr. Roux, 75724 Paris cedex 15, France.
authors.forename: Chiara
authors.initials: C
authors.lastname: Recchi
authors.forename: Bianca
authors.initials: B
authors.lastname: Sclavi
authors.forename: Jean
authors.initials: J
authors.lastname: Rauzier
authors.forename: Brigitte
authors.initials: B
authors.lastname: Gicquel
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Reyrat
mesh_terms: D020816:Amino Acid Motifs; D051777:AraC Transcription Factor; D001426:Bacterial Proteins; D001483:Base Sequence; D001665:Binding Sites; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D003850:Deoxyribonuclease I / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D008957:Models, Genetic; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D020102:Mycobacterium smegmatis / Q000378:metabolism; D009169:Mycobacterium tuberculosis / Q000378:metabolism*; D016366:Open Reading Frames; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000378:metabolism*; D014157:Transcription Factors / Q000737:chemistry* / Q000502:physiology*; D014158:Transcription, Genetic; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D051777:AraC Transcription Factor; D001426:Bacterial Proteins; D012097:Repressor Proteins; C477738:Rv1395 protein, Mycobacterium tuberculosis; D014157:Transcription Factors; D003577:Cytochrome P-450 Enzyme System; D003850:Deoxyribonuclease I; D001616:beta-Galactosidase