Site-specific DNA damage induced by UVA radiation in the presence of endogenous photosensitizer.

This paper summarizes our recent findings on the sequence-specific DNA damage induced by UVA radiation in the presence of various endogenous molecules. The Type I (electron transfer) mechanism can induce hydroxylation specifically at C-8 of guanine located 5' to guanine in double-stranded DNA. In contrast, the major Type II (singlet oxygen) mechanism can damage most guanines without sequence specificity. With the minor Type II (superoxide anion radical) mechanism, DNA damage could be induced via metal-mediated reactions. Active species generated in the presence of Cu(II) were shown to induce piperidine-labile lesions frequently at thymine. We discuss the sequence-specific DNA damage in relation to UVA carcinogenesis.