Characterization of two radiation-induced lesions from DNA: studies using nuclease P1

Exposure of DNA oligomers to ionizing radiation in oxygenated solution reveals that the two lesions formed in highest yield are the 8-hydroxy modification of guanine and the formamido remnant of thymine. The effect of these lesions on the hydrolysis of the phosphodiester bond by nuclease P1 was studied. Whereas the 8-hydroxyguanine lesion does not affect hydrolysis of the adjacent 3' phosphoester bond by nuclease P1, the formamido lesion markedly retards hydrolysis. Consistent with the oligomer results, digestion of irradiated DNA polymer by nuclease P1 plus acid phosphatase yielded the 8-hydroxyguanine lesion, obtained as the modified nucleoside, and the formamido lesion, obtained as a modified dinucleotide.