Difference in the Mechanisms of Poly(dT) Synthesis by DNA Polymerases1 β and γ2

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Abstract
Poly(dT) products which were synthesized depending on (rA)n·(dT)12–18 as a template primer by mammalian DNA polymerases βand γ were analyzed by alkaline sucrose gradient centrifugation. The size of the population of poly(dT) chains synthesized by DNA polymerase β increased slowly and consistently during incubation up to at least 30 min. On the other hand, the product size with DNA polymerase γ reached the final size (7 s) within 5 mm and the number of products increased during further incubation. Comparison of product number per enzyme molecule suggests that DNA polymerase β acts on multiple primers in a distributive fashion while DNA polymerase γ completes poly(dT) chains of large size in a one-by-one fashion.