Direct and indirect effects of UV radiation on DNA and its components

In this survey, emphasis was placed on the main photoreactions of nucleic a cid components, involving both direct and indirect effects. The main UVB- a nd UVA-induced DNA photoproducts, together with the mechanisms of their for mation, are described. Information on the photoproduct distribution within cellular DNA is also provided, taking into account the limitations of the d ifferent analytical methods applied to monitor the formation of the DNA dam age. Thus, the formation of the main DNA dimeric pyrimidine lesions produce d by direct absorption of UVB photons was assessed using a powerful HPLC-ta ndem mass spectrometry assay. In addition, it was found that UVA photooxida tion damage mostly involves the guanine residues of cellular DNA as the res ult of singlet oxygen generation by still unknown endogenous photosensitize rs. (C) 2001 Elsevier Science B.V. All rights reserved.