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PLoS One. 2015 Mar 26;10(3):e0122071. doi: 10.1371/journal.pone.0122071. eCollection 2015.

Protease activity of PprI facilitates DNA damage response: Mn2+-dependence and substrate sequence-specificity of the proteolytic reaction.

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Key Laboratory of Chinese Ministry of Agriculture for Nuclear-Agricultural Sciences, Institute of Nuclear-Agricultural Sciences, Zhejiang University, Hangzhou, China.
Zhejiang Key Laboratory of Radiation Oncology, Zhejiang Cancer Research Institute, Zhejiang Cancer Hospital, Hangzhou, China.
National Institute on Aging, Biomedical Research Center, National Institutes of Health, Baltimore, United States of America.


The extremophilic bacterium Deinococcus radiodurans exhibits an extraordinary resistance to ionizing radiation. Previous studies established that a protein named PprI, which exists only in the Deinococcus-Thermus family, acts as a general switch to orchestrate the expression of a number of DNA damage response (DDR) proteins involved in cellular radio-resistance. Here we show that the regulatory mechanism of PprI depends on its Mn(2+)-dependent protease activity toward DdrO, a transcription factor that suppresses DDR genes' expression. Recognition sequence-specificity around the PprI cleavage site is essential for DNA damage repair in vivo. PprI and DdrO mediate a novel DNA damage response pathway differing from the classic LexA-mediated SOS response system found in radiation-sensitive bacterium Escherichia coli. This PprI-mediated pathway in D. radiodurans is indispensable for its extreme radio-resistance and therefore its elucidation significantly advances our understanding of the DNA damage repair mechanism in this amazing organism.

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