Variable-number tandem repeat 3690 polymorphism in Indian clinical isolates of Mycobacterium tuberculosis and its influence on transcription.
Variable-number tandem repeat (VNTRs) occur throughout the chromosome of Mycobacterium tuberculosis. Although these polymorphic VNTRs, also known as mycobacterial interspersed repetitive units (MIRUs), have proved to be useful tools in molecular epidemiology, their biological significance is less well understood. This study investigated the polymorphism of the VNTR 3690 locus located in the intergenic region between rv3304 and rv3303c (encoding the gplD2 and lpdA genes, respectively) and its possible function in the regulation of gene expression. The copy number of VNTR 3690 was found to vary among Indian clinical isolates of M. tuberculosis (one to twelve copies), M. tuberculosis H37Rv TMC102 (four copies), M. tuberculosis H37Ra (two to four copies), Mycobacterium bovis BCG (one copy). The expression of lpdA as measured by quantitative RT-PCR was 12-fold higher in M. tuberculosis H37Rv than in M. bovis BCG. Using a GFP reporter system in which the 5'-flanking region of lpdA was fused to the gfp gene, the effect of VNTRs on gene expression was measured in an M. bovis BCG host background by real-time PCR. Compared with one VNTR repeat, a 12.5-fold upregulation of GFP expression was found with a flanking region containing four VNTR 3690 repeats, indicating that there is a good correlation between VNTR copy number and transcription of lpdA.
Microbiology Division, Central Drug Research Institute, Lucknow 226001, India.
Parvez
P
Akhtar
Department of Laboratory Medicine, All India Institute of Medical Sciences, New Delhi, India.
Sarman
S
Singh
Molecular Pathology of Tuberculosis, Pasteur Institute, Brussels, Belgium.
Pablo
P
Bifani
Microbiology Division, Central Drug Research Institute, Lucknow 226001, India.
Satinder
S
Kaur
Microbiology Division, Central Drug Research Institute, Lucknow 226001, India.
Brahm S
BS
Srivastava
Microbiology Division, Central Drug Research Institute, Lucknow 226001, India.
Ranjana
R
Srivastava
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D021901:DNA, Intergenic / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007194:India; D018598:Minisatellite Repeats / Q000235:genetics*; D008969:Molecular Sequence Data; D009169:Mycobacterium tuberculosis / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D011110:Polymorphism, Genetic; D014158:Transcription, Genetic; D014397:Tuberculosis, Pulmonary / Q000382:microbiology; D015854:Up-Regulation
D001426:Bacterial Proteins; D021901:DNA, Intergenic; D049452:Green Fluorescent Proteins; D010088:Oxidoreductases