title: Macrophage-specific Mycobacterium tuberculosis genes: identification by green fluorescent protein and kanamycin resistance selection.
abstract: Mycobacterium tuberculosis survives and multiplies inside macrophages of its host by modulating the expression of several genes essential for in vivo survival. An in vivo expression system has been developed, based on green fluorescent protein and kanamycin resistance, to identify M. tuberculosis genes which appear to be up-regulated in infected macrophages. A promoter-trap shuttle vector, pLL192, was constructed, containing a streptomycin resistance gene as selection marker and an artificial bicistronic operon composed of the promoterless green fluorescent protein (gfp) gene, followed by the kanamycin resistance gene. A unique BamHI site upstream of the gfp gene allowed for insertion of promoter libraries. The vector was validated by the use of known regulated or constitutive M. tuberculosis promoters. In addition, an M. tuberculosis genomic DNA library was inserted into pLL192 and then introduced into Mycobacterium bovis BCG. The recombinant BCG cells were then used to infect the J774A.1 murine macrophage-like cell line in the presence of kanamycin. Several recombinant BCG cells were thereby selected that were resistant to kanamycin within infected macrophages, but were sensitive to kanamycin when grown in vitro. The kanamycin resistance phenotype was paralleled by the fluorescence phenotype. After nucleotide sequencing, the corresponding genes were identified as mce1A, PE_PGRS63(RV3097c), Rv2232, Rv1026, Rv1635c, viuB, Rv2231(cobC) and Rv0997. Real-time PCR analysis using RNA isolated at various time points from M. tuberculosis and M. bovis BCG grown in vitro and within macrophages, confirmed the up-regulation of these genes. The level of up-regulation varied from 2- to 40-fold in macrophages compared to growth in vitro.
authors.affiliation: Microbiology Division, Central Drug Research Institute, Lucknow, India.
authors.forename: Vikas
authors.initials: V
authors.lastname: Srivastava
authors.affiliation: INSERM U629, Institut Pasteur de Lille, 1 rue du Professor Calmette, F-59019 Lille Cedex, France.
authors.forename: Carine
authors.initials: C
authors.lastname: Rouanet
authors.affiliation: Microbiology Division, Central Drug Research Institute, Lucknow, India.
authors.forename: Ranjana
authors.initials: R
authors.lastname: Srivastava
authors.affiliation: INSERM U629, Institut Pasteur de Lille, 1 rue du Professor Calmette, F-59019 Lille Cedex, France.
authors.forename: B
authors.initials: B
authors.lastname: Ramalingam
authors.affiliation: INSERM U629, Institut Pasteur de Lille, 1 rue du Professor Calmette, F-59019 Lille Cedex, France.
authors.forename: Camille
authors.initials: C
authors.lastname: Locht
authors.affiliation: Microbiology Division, Central Drug Research Institute, Lucknow, India.
authors.forename: Brahm S
authors.initials: BS
authors.lastname: Srivastava
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics*; D000818:Animals; D002460:Cell Line; D004269:DNA, Bacterial / Q000235:genetics; D020869:Gene Expression Profiling / Q000379:methods*; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000032:analysis / Q000235:genetics; D007613:Kanamycin Resistance; D008264:Macrophages / Q000382:microbiology*; D051379:Mice; D009163:Mycobacterium bovis / Q000235:genetics; D009169:Mycobacterium tuberculosis / Q000235:genetics* / Q000276:immunology*; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D012329:RNA, Bacterial / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D017422:Sequence Analysis, DNA; D015854:Up-Regulation
chemical_list: D004269:DNA, Bacterial; D012329:RNA, Bacterial; D012333:RNA, Messenger; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins