In situ repair of cyclobutane pyrimidine dimers and 6-4 photoproducts in human skin exposed to solar simulating radiation

DNA repair is crucial to the integrity of the human genome. The ultraviolet radiation portion of solar radiation is responsible for the rising inciden ce of skin cancer, one of the most common types of cancer in humans. We app lied a recently developed P-32-post-labeling technique to measure the in si tu DNA repair efficiency of solar-simulated radiation induced cyclobutane p yrimidine dimers and 6-4 photoproducts in the skin of nine healthy voluntee rs with skin type II. Our results show about 6-fold interindividual variati ons in the level of DNA damage after exposure to an equal biologic dose - 2 minimal erythema doses. The kinetics of DNA repair indicated a base sequen ce dependence of the repair process. The DNA repair efficiency showed a 20- fold difference in volunteers. an age-related decrease of DNA repair capaci ty was observed; however, the data are limited due to a small number of sub jects and a narrow age range. The variable response in DNA damage levels an d individual differences in DNA repair efficiency suggest a susceptible sub group of people probably with a higher skin cancer risk.