ENZYMATIC EXCISION OF RADIATION-INDUCED LESIONS FROM DNA MODEL COMPOUNDS

Dinucleoside monophosphates in which the 5' nucleoside contained a radiation-modified base were tested as substrates to bovine spleen phosphodiesterase (SPD) and snake venom phosphodiesterase. The radiation-modified bases included thymine glycols, 5-hydroxymethyluracil, 8-hydroxyguanine, and a formamido remnant of thymine. The lesions had widely different effects on diesterase action, varying from little inhibition, as in the case of digestion of dT*pA by SPD, where T* is the hydroxymethyluracil modification, to severe inhibition, as in the case of digestion of dG*pC by SPD, where G* is the 8-hydroxyguanine modification.