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Biochem Biophys Res Commun. 2008 Feb 29;367(1):213-8. doi: 10.1016/j.bbrc.2007.12.124. Epub 2007 Dec 28.

Mycoplasmas regulate the expression of heat-shock protein genes through CIRCE-HrcA interactions.

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Department of Life Science, Institute of Biotechnology, National Dong Hwa University, 1 University Street, Hualien, Taiwan 974, ROC.


Mycoplasmas in general are rarely exposed to severe environmental changes except during its colonization and infection processes. Genomic analysis indicates that Mycoplasma hyopneumoniae possesses the genes of a single sigma factor and the HrcA repressor of negative regulation of the heat-shock response. A perfect inverted repeat sequence (5'-CTGGCACTT-N(9)-AAGTGCCAA-3') upstream of the DnaK gene has also been identified. In the present study, we demonstrate the functionality of HrcA-CIRCE interactions using the gel electrophoretic mobility shift assay. The presence of the unique sigma factor, HrcA repressor, and the CIRCE-like sequences reveals that mycoplasmal species may all use the negative regulatory mechanism in the heat-shock response. It is conceivable that mycoplasmas may have evolved a single HrcA repressor-based mechanism which might be the most simple and economical way of controlling HSP gene expression.

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