Differential utilization of 2', 3'-dideoxyguanosine 5'-triphosphate as a substrate for various DNA polymerases

Abstract

2', 3'-dideoxyguanosine 5'-triphosphate (ddGTP) was found to be an efficient substrate for DNA polymerase β when activated DNA was used as the template · primer. Under the optimized reaction conditions with activated DNA, the rate of the incorporation of ddGTP into DNA was almost equal to that of the corresponding normal substrate dGTP The Km value for ddGTP (1.8 μM) was smaller than that for dGTP (7.8 μM). In contrast, ddGTP was not utilized as a substrate for DNA polymerase γ with any of activated DNA and (dC) n · (dG) 12–18 as the template primer. Other DNA polymerases such as DNA polymerase α, E coli DNA polymerase I and retroviral reverse transcriptase could poorly utilize ddGTP as a substrate. Some of the kinetic properties of DNA polymerase β revealed toward ddGTP are also described. Since DNA polymerase β plays a role in DNA repair, the present results predict possible appearance of cytotoxicity or clinical side effect(s) of 2', 3'-dideoxyguanosine (ddG), known as a potent inhibitor of human immunodeficiency viras, when ddG is administered to the patients with acquired immune deficiency syndrome (AIDS) or AIDS-related complex.