DNA的复制和转录通常在体内同时发生。在DNA链上用于进行DNA复制的DNA合成酶与用于转录的RNA合成酶迎头碰撞会使DNA合成过程停止，但一个复制体（replisome）碰到一个在DNA模板上沿同一方向工作的一个RNA聚合酶会发生什么情况呢？
美国洛克菲勒大学的Richard Pomerantz 和 Mike O’Donnell发现，复制体（一种集聚合与校对活性于一身的多酶复合物）碰到障碍时可以灵活完成自己的任务。RNA聚合酶被从DNA中移走，但复制体和新生成的mRNA仍然附着在其上。一个复制组装因子（beta clamp）会找到mRNA的3\'端，并与仍然结合在一起的复制体相连，后者利用mRNA作为一个引子来重新启动DNA的合成。（生物谷Bioon.com）
生物谷推荐原始出处：
Nature 456, 762-766 (11 December 2008) | doi:10.1038/nature07527
The replisome uses mRNA as a primer after colliding with RNA polymerase
Richard T. Pomerantz1 & Mike O'Donnell1
The Rockefeller University, Howard Hughes Medical Institute, 1230 York Avenue, New York, New York 10021, USA
Replication forks are impeded by DNA damage and protein–nucleic acid complexes such as transcribing RNA polymerase. For example, head-on collision of the replisome with RNA polymerase results in replication fork arrest. However, co-directional collision of the replisome with RNA polymerase has little or no effect on fork progression. Here we examine co-directional collisions between a replisome and RNA polymerase in vitro. We show that the Escherichia coli replisome uses the RNA transcript as a primer to continue leading-strand synthesis after the collision with RNA polymerase that is displaced from the DNA. This action results in a discontinuity in the leading strand, yet the replisome remains intact and bound to DNA during the entire process. These findings underscore the notable plasticity by which the replisome operates to circumvent obstacles in its path and may explain why the leading strand is synthesized discontinuously in vivo.
