32P-postlabeling of N-7, N2 and O6 2'-deoxyguanosine 3'-monophosphate adducts of styrene oxide

Adducts were prepared by reacting styrene oxide with 2-deoxyguanosine 3'-monophosphate (dGMP). Four isomeric N-7-, two diastereomeric N2- and three isomeric O6-adduct were isolated and characterized. The adducts were used as substrates in the 32P-postlabeling reaction. No phosphorylation products were seen with the N-7-alkylation products. One diastereomeric N2-adduct was labeled with 20% efficiency and the second with a markedly lower efficiency. Two of the three O6-adducts were labeled with 5% and the third with 10% labeling efficiency. The results suggest that large N-7-dGMP adducts are very poor substrates of T4 polynucleotide kinase. The diastereomeric products are labeled at different efficiencies indicating stereoselectivity in the kinase reaction.