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通过五个 cryoEM 结构揭示了人类起源识别复合物的动态性质。

The dynamic nature of the human origin recognition complex revealed through five cryoEM structures.

机构信息

W. M. Keck Structural Biology Laboratory, New York, United States.

Howard Hughes Medical Institute, New York, United States.

出版信息

Elife. 2020 Aug 18;9:e58622. doi: 10.7554/eLife.58622.

Abstract

Genome replication is initiated from specific origin sites established by dynamic events. The Origin Recognition Complex (ORC) is necessary for orchestrating the initiation process by binding to origin DNA, recruiting CDC6, and assembling the MCM replicative helicase on DNA. Here we report five cryoEM structures of the human ORC (HsORC) that illustrate the native flexibility of the complex. The absence of ORC1 revealed a compact, stable complex of ORC2-5. Introduction of ORC1 opens the complex into several dynamic conformations. Two structures revealed dynamic movements of the ORC1 AAA+ and ORC2 winged-helix domains that likely impact DNA incorporation into the ORC core. Additional twist and pinch motions were observed in an open ORC conformation revealing a hinge at the ORC5·ORC3 interface that may facilitate ORC binding to DNA. Finally, a structure of ORC was determined with endogenous DNA bound in the core revealing important differences between human and yeast origin recognition.

摘要

基因组复制是从由动态事件建立的特定起始位点开始的。原点识别复合物(ORC)通过与原点 DNA 结合、招募 CDC6 和在 DNA 上组装 MCM 复制解旋酶,来协调起始过程,这是必不可少的。在这里,我们报告了五个人类 ORC(HsORC)的冷冻电镜结构,这些结构说明了该复合物的固有灵活性。缺少 ORC1 揭示了一个紧凑、稳定的 ORC2-5 复合物。引入 ORC1 后,复合物会打开成几种动态构象。两个结构显示了 ORC1 AAA+和 ORC2 翼状螺旋结构域的动态运动,这可能会影响 DNA 整合到 ORC 核心中。在开放的 ORC 构象中观察到额外的扭曲和挤压运动,揭示了 ORC5·ORC3 界面处的铰链,这可能有助于 ORC 与 DNA 结合。最后,确定了与核心中结合的内源性 DNA 的 ORC 结构,揭示了人类和酵母原点识别之间的重要差异。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/57af/7467728/65ba8beb58ee/elife-58622-fig1.jpg

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