Tuberculosis 2015-09-01

Genetic and chemical validation identifies Mycobacterium tuberculosis topoisomerase I as an attractive anti-tubercular target.

Sudha Ravishankar, Anisha Ambady, Disha Awasthy, Naina Vinay Mudugal, Sreenivasaiah Menasinakai, Sandesh Jatheendranath, Supreeth Guptha, Sreevalli Sharma, Gayathri Balakrishnan, Radha Nandishaiah, Vasanthi Ramachandran, Charles J Eyermann, Folkert Reck, Suresh Rudrapatna, Vasan K Sambandamurthy, Umender K Sharma

Index: Tuberculosis (Edinb.) 95 , 589-98, (2015)

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Abstract

DNA topoisomerases perform the essential function of maintaining DNA topology in prokaryotes. DNA gyrase, an essential enzyme that introduces negative supercoils, is a clinically validated target. However, topoisomerase I (Topo I), an enzyme responsible for DNA relaxation has received less attention as an antibacterial target, probably due to the ambiguity over its essentiality in many organisms. The Mycobacterium tuberculosis genome harbors a single topA gene with no obvious redundancy in its function suggesting an essential role. The topA gene could be inactivated only in the presence of a complementing copy of the gene in M. tuberculosis. Furthermore, down-regulation of topA in a genetically engineered strain of M. tuberculosis resulted in loss of bacterial viability which correlated with a concomitant depletion of intracellular Topo I levels. The topA knockdown strain of M. tuberculosis failed to establish infection in a murine model of TB and was cleared from lungs in two months post infection. Phenotypic screening of a Topo I overexpression strain led to the identification of an inhibitor, thereby providing chemical validation of this target. Thus, our work confirms the attractiveness of Topo I as an anti-mycobacterial target.Copyright © 2015 Elsevier Ltd. All rights reserved.