期刊
JOURNAL OF GENETICS
卷 80, 期 3, 页码 119-124出版社
INDIAN ACADEMY SCIENCES
DOI: 10.1007/BF02717907
关键词
DNA curvature; supercoiling; DNA topology; gyrase; relaxation-stimulated transcription
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.
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