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Axial distortion as a sensor of supercoil changes: a molecular model for the homeostatic regulation of DNA gyrase

Unniraman, Shyam and Nagaraja, Valakunja (2001) Axial distortion as a sensor of supercoil changes: a molecular model for the homeostatic regulation of DNA gyrase. In: Journal of Genetics, 80 (3). pp. 119-124.

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Abstract

Negative supercoiling stimulates transcription of many genes. In contrast, transcription of the genes coding for DNA gyrase is subject to a novel mechanism of autoregulation, wherein relaxation of the template DNA stimulates their transcription. Since DNA gyrase is the sole supercoiling activity in the eubacterial cell, relaxation-stimulated transcription (RST) could reflect an autoregulatory mechanism to maintain supercoil levels within the cell. Extensive deletion and mutational analyses of Escherichia coli gyrA promoter have shown that the -10 region is essential for RST; however, a molecular model has proved to be elusive. We find a strong bend centre immediately downstream of the -10 region in the gyrA promoter. On the basis of analysis of various mutants in the -10 region, we propose a model where axial distortion acts as a sensor of topological changes in DNA. Our model is consistent with earlier data with E. coli gyrA and gyrB promoters. We also extrapolate the model to explain the phenomenon of RST of gyr promoters in other organisms and contrast it with promoters induced by supercoiling.

Item Type: Journal Article
Additional Information: Copyright for this article belongs to Indian Academy of Sciences.
Keywords: DNA curvature;supercoiling;DNA topology;gyrase;relaxation-stimulated transcription
Department/Centre: Division of Biological Sciences > Microbiology & Cell Biology
Date Deposited: 09 Sep 2004
Last Modified: 19 Sep 2010 04:16
URI: http://eprints.iisc.ernet.in/id/eprint/2031

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