Effects of 2',3'-dideoxythymidine triphosphate on replicative DNA synthesis and unscheduled DNA synthesis in permeable mouse sarcoma cells

2',3'-Dideoxythymidine triphosphate differentially inhibited replicative DNA synthesis in permeable mouse ascites sarcoma cells and unscheduled DNA synthesis in bleomycin-treated permeable cells or in isolated rat liver nuclei. The mode of inhibition of 2',3'-dideoxythymidine triphosphate was competitive with respect to deoxythymidine triphosphate. 2',3'-Dideoxythymidine triphosphate inhibited replicative DNA synthesis with a Ki of 8 microM, whereas unscheduled DNA synthesis was more sensitive, the Ki being 0.5 microM. Referring to the differential sensitivity of DNA polymerases alpha and beta to 2',3'-dideoxythymidine triphosphate and to other related information reported previously, the present results suggested that DNA polymerase alpha is playing a major role in replicative DNA synthesis, and DNA polymerase beta in unscheduled DNA synthesis.