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Rewired Downregulation of DNA Gyrase Impacts Cell Division, Expression of Topology Modulators, and Transcription in Mycobacterium smegmatis

Guhal, Sarmistha and Udupa, Shubha and Ahmed, Wareed and Nagaraja, Valakunja (2018) Rewired Downregulation of DNA Gyrase Impacts Cell Division, Expression of Topology Modulators, and Transcription in Mycobacterium smegmatis. In: JOURNAL OF MOLECULAR BIOLOGY, 430 (24). pp. 4986-5001.

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Official URL: https://doi.org/10.1016/j.jmb.2018.10.001


DNA gyrase, essential for DNA replication and transcription, has traditionally been studied in vivo by treatments that inhibit the enzyme activity. Due to its indispensable function, gyrA and gyrB deletions cannot be generated. The coumarin inhibitors of gyrase induce the supercoiling-sensitive gyrase promoter by a mechanism termed relaxation-stimulated transcription. Hence, to study the effect of sustained reduction in gyrase levels, a conditional-knockdown strain was generated in Mycobacterium smegmatis such that gyrase expression was controlled by a supercoiling non-responsive regulatory circuit. Decreasing intracellular gyrase protein levels beyond 50% affected cell growth. Reduced gyrase levels in the reprogrammed gyr operon caused chromosome relaxation, diffuse nucleoid structure, cell elongation, and altered gene expression. The key cell division protein, ftsZ, was severely reduced in the elongated cells, indicating a link between gyrase and cell division. Low levels of gyrase resulted in low compensatory expression of topoisomerase I and elevated expression of topology modulators hupB and Isr2. Altered supercoiling due to gyrase depletion caused corresponding changes in the RNA polymerase density on transcription units leading to their altered transcription. The enhanced susceptibility of the knockdown strain to anti-tubercular drugs suggests its utility for screening new molecules that may act synergistically with gyrase inhibitors. (C) 2018 Published by Elsevier Ltd.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
Keywords: DNA supercoiling; conditional knockdown; relaxation-stimulated transcription; supercoiling-sensitive promoters; RNA polymerase
Department/Centre: Division of Biological Sciences > Microbiology & Cell Biology
Date Deposited: 28 Jan 2019 09:25
Last Modified: 28 Jan 2019 09:25
URI: http://eprints.iisc.ac.in/id/eprint/61488

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