How does circadian rhythm affect DNA repair?
My research has shown that the circadian clock directly regulates the efficiency of nucleotide excision repair. In mice, I demonstrated that the XPA protein, a key damage recognition factor, is expressed in a daily rhythm controlled by the clock genes CLOCK and BMAL1. As a result, UV-induced DNA damage is repaired more efficiently during the day than at night. This has practical implications: if you apply a carcinogen to mouse skin at different times, tumors develop faster when exposure occurs at night. In humans, this suggests that sun exposure timing matters—getting sunburned in the evening might be riskier than in the morning. I also found that cryptochromes, which are part of the clock mechanism, evolved from photolyase, linking light sensing to repair. In science, there are no shortcuts, and this connection between our internal timekeeper and genome maintenance is a beautiful example of molecular integration.
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