M. tuberculosis (Mtb) is one of the leading causes of death worldwide and claims millions of lives annually. Approximately 1.7 billion people worldwide are asymptomatically infected with the tubercle bacillus and constitute a major impediment to worldwide public health control measures. Previous work had shown that a point mutation (Arg515->His) in the 4.2 domain of RpoV, the principal sigma factor in Mycobacterium bovis, is attenuating. Using the yeast two-hybrid system, we have established that the 4.2 domain of virulent Mtb specifically interacts with a regulatory protein WhiB3. In contrast, the attenuated RpoV allele containing the single point mutation was unable to interact with WhiB3. We constructed a Mtb whiB3 mutant (deltawhiB3) and showed that it behaved identical to the wild-type strain with respect to its ability to replicate in mice and guinea pigs in vivo. Mice infected with AwhiB3 showed significantly longer survival times than mice infected with the wild type Mtb. In addition, the lungs of AwhiB3-infected mice appeared much less adversely affected. It is notable that this virulence gene would not have been detected using conventional screens such as signature tagged mutagenesis, which screens for mutants primarily defective in growth, and not virulence. Furthermore, we have shown that a whiB3 mutant of virulent M. bovis, in contrast to AwhiB3, was completely attenuated for growth in guinea pigs. Mtb contain seven WhiB homologues that show strong homology to proteins that are critical for sporulation in Streptomyces spp. We hypothesize that WhiB3 regulates the expression of mycobacterial components that modulate the host immune system. To better understand the mechanism of whiB3 in Mtb virulence, we will use electron paramagnetic resonance spectroscopy (EPR) to biochemically characterize the WhiB3 Fe-S cluster genes, identify genes under WhiB3 control, and characterize proteins that interact with the WhiB family. We will also demonstrate that WhiB3 is a DNA binding protein capable of activating transcription of specific target genes. We will study the in vivo expression of the whiB family and their role in virulence. These studies will characterize the WhiB family as potential targets for interventions that may abolish virulence, but not growth. These studies will also provide insight into understanding whether TB is an anomalous immunological reaction in response to the persistent bacilli, whether the bacilli themselves induce lethal immunopathology, or if it is a combination of both.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
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Bacteriology and Mycology Subcommittee 2 (BM)
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Sizemore, Christine F
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University of Alabama Birmingham
Schools of Medicine
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Saini, Vikram; Cumming, Bridgette M; Guidry, Loni et al. (2016) Ergothioneine Maintains Redox and Bioenergetic Homeostasis Essential for Drug Susceptibility and Virulence of Mycobacterium tuberculosis. Cell Rep 14:572-585
Lamprecht, Dirk A; Finin, Peter M; Rahman, Md Aejazur et al. (2016) Turning the respiratory flexibility of Mycobacterium tuberculosis against itself. Nat Commun 7:12393
Chinta, Krishna C; Saini, Vikram; Glasgow, Joel N et al. (2016) The emerging role of gasotransmitters in the pathogenesis of tuberculosis. Nitric Oxide 59:28-41
Gopal, Radha; Monin, Leticia; Torres, Diana et al. (2013) S100A8/A9 proteins mediate neutrophilic inflammation and lung pathology during tuberculosis. Am J Respir Crit Care Med 188:1137-46
Saini, Vikram; Farhana, Aisha; Steyn, Adrie J C (2012) Mycobacterium tuberculosis WhiB3: a novel iron-sulfur cluster protein that regulates redox homeostasis and virulence. Antioxid Redox Signal 16:687-97
Saini, Vikram; Farhana, Aisha; Glasgow, Joel N et al. (2012) Iron sulfur cluster proteins and microbial regulation: implications for understanding tuberculosis. Curr Opin Chem Biol 16:45-53
Chawla, Manbeena; Parikh, Pankti; Saxena, Alka et al. (2012) Mycobacterium tuberculosis WhiB4 regulates oxidative stress response to modulate survival and dissemination in vivo. Mol Microbiol 85:1148-65
Farhana, Aisha; Saini, Vikram; Kumar, Ashwani et al. (2012) Environmental heme-based sensor proteins: implications for understanding bacterial pathogenesis. Antioxid Redox Signal 17:1232-45
Kumar, Ashwani; Farhana, Aisha; Guidry, Loni et al. (2011) Redox homeostasis in mycobacteria: the key to tuberculosis control? Expert Rev Mol Med 13:e39
Mai, Deborah; Jones, Jennifer; Rodgers, John W et al. (2011) A screen to identify small molecule inhibitors of protein-protein interactions in mycobacteria. Assay Drug Dev Technol 9:299-310

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