Matsukage A, Nishizawa M, Takahashi T, Hozumi T
J Biochem. 1980 Dec;88(6):1869-77.
The DNA chain elongation mechanisms of mouse DNA polymerases alpha and beta have been analyzed by using denatured DNA with a (dT)n block at the 3'-end as a template in combination with RNA ((rA)12-20)primer. The (rA)12-20-primed DNA product synthesized by DNA polymerase alpha was 3-5 s in size even after prolonged reaction; instead of a size increase, the number of 3-5 s molecules increased with the reaction time. The size of products was not affected by differences in 3H-labeled substrate (dATP or dTTP), enzyme amount, KCl concentration, or the length of 3'-(dT)n blocks. On the other hand, DNA polymerase beta synthesized long DNA products by a highly distributive reaction mechanism. 3-5 sDNA pieces synthesized by DNA polymerase alpha were not elongated any further by DNA polymerase alpha, but were converted into long DNA chains by DNA polymerase beta. The results imply that DNA polymerase alpha recognizes the size of the product DNA, and shuts off further elongation.
通过使用在3'-末端带有(dT)n阻断的变性DNA作为模板，并结合RNA((rA)12 - 20)引物，对小鼠DNA聚合酶α和β的DNA链延伸机制进行了分析。即使经过长时间反应，由DNA聚合酶α合成的(rA)12 - 20引发的DNA产物大小仍为3 - 5个核苷酸；产物大小没有增加，而是3 - 5个核苷酸的分子数量随反应时间增加。产物大小不受3H标记底物(dATP或dTTP)、酶量、KCl浓度或3'-(dT)n阻断长度差异的影响。另一方面，DNA聚合酶β通过高度分布的反应机制合成了长DNA产物。由DNA聚合酶α合成的3 - 5个核苷酸的DNA片段不会被DNA聚合酶α进一步延伸，但会被DNA聚合酶β转化为长DNA链。结果表明，DNA聚合酶α识别产物DNA的大小，并停止进一步延伸。
