Visible light induced DNA cleavage by the hybrid antitumor antibiotic dynemicin A.

Dynemicin A, which is a hybrid antitumor antibiotic containing anthraquinone and enediyne cores, effectively breaks DNA strands upon irradiation with visible light of long wavelength. The preferential cutting sites of visible light induced DNA cleavage with dynemicin A are on the 3'-side of purine bases such as in 5'-AT and 5'-GT sequences. The observed nucleotide cutting specificity is remarkably similar to that of NADPH- (or thiol) induced DNA breakage with dynemicin A, suggesting the presence of the same DNA-cleaving intermediate. Indeed, the photoproduct of dynemicin A is chromatographically identical with the reaction product (dynemicin H) of the thiol-activated dynemicin A. On the basis of the present results, a reasonable mechanism for the visible light induced DNA cleavage of dynemicin A has been proposed.