Tocilj Ante, On Kin Fan, Yuan Zuanning, Sun Jingchuan, Elkayam Elad, Li Huilin, Stillman Bruce, Joshua-Tor Leemor
W. M. Keck Structural Biology Laboratory, Cold Spring Harbor, New York, United States.
Howard Hughes Medical Institute, Cold Spring Harbor, New York, United States.
Elife. 2017 Jan 23;6:e20818. doi: 10.7554/eLife.20818.
Binding of the Origin Recognition Complex (ORC) to origins of replication marks the first step in the initiation of replication of the genome in all eukaryotic cells. Here, we report the structure of the active form of human ORC determined by X-ray crystallography and cryo-electron microscopy. The complex is composed of an ORC1/4/5 motor module lobe in an organization reminiscent of the DNA polymerase clamp loader complexes. A second lobe contains the ORC2/3 subunits. The complex is organized as a double-layered shallow corkscrew, with the AAA+ and AAA+-like domains forming one layer, and the winged-helix domains (WHDs) forming a top layer. CDC6 fits easily between ORC1 and ORC2, completing the ring and the DNA-binding channel, forming an additional ATP hydrolysis site. Analysis of the ATPase activity of the complex provides a basis for understanding ORC activity as well as molecular defects observed in Meier-Gorlin Syndrome mutations.
起始识别复合物（ORC）与复制起点的结合标志着所有真核细胞中基因组复制起始的第一步。在此，我们报告了通过X射线晶体学和冷冻电子显微镜确定的人源ORC活性形式的结构。该复合物由一个ORC1/4/5运动模块叶组成，其结构类似于DNA聚合酶钳位装载复合物。第二个叶包含ORC2/3亚基。该复合物被组织成双层浅螺旋结构，其中AAA+和类AAA+结构域形成一层，而翼状螺旋结构域（WHD）形成顶层。CDC6很容易装配在ORC1和ORC2之间，完成环和DNA结合通道，形成一个额外的ATP水解位点。对该复合物ATP酶活性的分析为理解ORC活性以及在迈耶-戈林综合征突变中观察到的分子缺陷提供了基础。
