Axial distortion as a sensor of supercoil changes: a molecular model for the homeostatic regulation of DNA gyrase.
J Genet
;
2001 Dec; 80(3): 119-24
Article
in English
| IMSEAR
| ID: sea-114504
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 anmd 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.
Full text:
Available
Index:
IMSEAR (South-East Asia)
Main subject:
Templates, Genetic
/
Algorithms
/
DNA, Superhelical
/
DNA Mutational Analysis
/
Molecular Sequence Data
/
Base Sequence
/
Models, Molecular
/
Gene Expression Regulation, Bacterial
/
Gene Expression Regulation, Enzymologic
/
Transcriptional Activation
Language:
English
Journal:
J Genet
Year:
2001
Type:
Article
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