The differential lysis of phosphoester bonds by nuclease P1

The hydrolysis by nuclease P1 of the 16 common deoxydinucleoside monophosphates was examined. The rates of hydrolysis of phosphodiester bond differ by more than two orders of magnitude; dinucleotide monophosphates of the type d(TpN) being most resistant and d(GpN) being next most resistant. The profiles of a mixture of the 16 common dinucleoside monophosphates and of DNA after partial hydrolysis by nuclease P1 and simultaneous treatment with acid phosphatase were compared. The resultant profiles are very similar, except for the appearance of 5-methyldeoxycytidine in the latter. Similar profiles are also obtained from a mixture of dinucleoside monophosphates and from DNA exposed to ionizing radiation beforehand. The 8-hydroxyguanine lesion and a formamido remnant of thymine appear in both profiles as a modified nucleoside and as modified dinucleoside monophosphate respectively. These results suggest that certain radiation induced DNA lesions can be selectively postlabelled based on their resistance to hydrolysis by nuclease P1. The nature of the nuclease P1-substrate interaction is discussed.