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复制叉由CMG螺旋酶中的单链DNA门激活
作者:小柯机器人 发布时间:2019/7/30 13:35:23

美国洛克菲勒大学Shixin Liu团队在研究中取得进展。他们揭示了复制叉是由CMG解旋酶中的单链DNA门激活的。 2019年7月25日,国际知名学术期刊《细胞》发表了这一成果。

通过对相关的单分子荧光和力显微镜观察,课题组研究人员发现CMG含有一个ssDNA门,可以实现单链和双链DNA之间的转换。当CMG与DNA聚合酶偶联时,CMG保持在单链DNA上,但当不偶联时,CMG利用这个门穿过双链DNA上的叉状连接。令人惊讶的是,CMG在双链DNA上经历了快速扩散,并能转变回单链DNA,形成一个功能复制体。这个门是CMG固有的,它不同于用于最初负载的Mcm2/5;然而,Mcm10通过增强CMG对DNA的亲和力来促进链的传代。这一门控过程可以解释CMG在起源时的双链DNA到单链DNA的转变,并有助于在叉形修复过程中保护双链DNA上的CMG。

研究人员表示,真核复制螺旋酶CMG最初是一个在双链DNA周围的封闭环,但必须转变为单链DNA才能发挥螺旋酶的作用。CMG还必须处理修复中间产物,例如缺少单链DNA的反向叉。

附:英文原文

Title: Replication Fork Activation Is Enabled by a Single-Stranded DNA Gate in CMG Helicase

Author: Michael R. Wasserman, Grant D. Schauer, Michael E. O’Donnell, Shixin Liu

Issue&Volume: 25 JULY 2019

Abstract: The eukaryotic replicative helicase CMG is a closed ring around double-stranded (ds)DNA at origins yet must transition to single-stranded (ss)DNA for helicase action. CMG must also handle repair intermediates, such as reversed forks that lack ssDNA. Here, using correlative single-molecule fluorescence and force microscopy, we show that CMG harbors a ssDNA gate that enables transitions between ss and dsDNA. When coupled to DNA polymerase, CMG remains on ssDNA, but when uncoupled, CMG employs this gate to traverse forked junctions onto dsDNA. Surprisingly, CMG undergoes rapid diffusion on dsDNA and can transition back onto ssDNA to nucleate a functional replisome. The gate—distinct from that between Mcm2/5 used for origin loading—is intrinsic to CMG; however, Mcm10 promotes strand passage by enhancing the affinity of CMG to DNA. This gating process may explain the dsDNA-to-ssDNA transition of CMG at origins and help preserve CMG on dsDNA during fork repair.

DOI: DOI:https://doi.org/10.1016/j.cell.2019.06.032

Source: https://www.cell.com/cell/fulltext/S0092-8674(19)30735-4#

期刊信息
Cell:《细胞》,创刊于1974年。隶属于细胞出版社,最新IF:36.216
官方网址:https://www.cell.com/