Structure of human Cdc45 and implications for CMG helicase function.
Structure of human Cdc45 and implications for CMG helicase function.
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DOI：
10.1038/ncomms11638
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发表时间：
2016-05-18
影响因子：
16.6
通讯作者：
Pellegrini L
中科院分区：
文献类型：
--
作者：
Simon AC;Sannino V;Costanzo V;Pellegrini L
细胞分裂周期蛋白 45 (Cdc45) 是基因组复制过程中 DNA 合成所必需的，作为 Cdc45-MCM-GINS (CMG) 解旋酶的组成部分。尽管其具有重要的生物学功能，但其在 DNA 复制中的生化作用仍然难以捉摸。在这里，我们报告了人类 Cdc45 的 2.1-Å 晶体结构，该结构证实了其与细菌 RecJ 核酸酶的进化联系，并揭示了支撑其在真核 DNA 复制中功能的几个意想不到的特征。其中包括 N 端和 C 端 DHH 结构域之间的长程相互作用，阻止进入其 RecJ 样折叠的 DNA 结合槽，以及其 N 端 DHH 结构域中的螺旋插入，这似乎准备进行复制体相互作用。结合现有的电子显微镜数据，我们通过突变分析验证了 Cdc45 与 MCM 环和 GINS 共激活剂关联的机制，这对于 CMG 组装至关重要。这些发现为合理化 Cdc45 在基因组复制中的重要作用提供了不可或缺的分子基础。 细胞周期分裂蛋白 Cdc45 是真核生物基因组复制所必需的。在这里，作者确定了人类 Cdc45 的晶体结构，并将其与功能数据相结合，以加深我们对其在 DNA 复制中的作用的理解。
Cell division cycle protein 45 (Cdc45) is required for DNA synthesis during genome duplication, as a component of the Cdc45-MCM-GINS (CMG) helicase. Despite its essential biological function, its biochemical role in DNA replication has remained elusive. Here we report the 2.1-Å crystal structure of human Cdc45, which confirms its evolutionary link with the bacterial RecJ nuclease and reveals several unexpected features that underpin its function in eukaryotic DNA replication. These include a long-range interaction between N- and C-terminal DHH domains, blocking access to the DNA-binding groove of its RecJ-like fold, and a helical insertion in its N-terminal DHH domain, which appears poised for replisome interactions. In combination with available electron microscopy data, we validate by mutational analysis the mechanism of Cdc45 association with the MCM ring and GINS co-activator, critical for CMG assembly. These findings provide an indispensable molecular basis to rationalize the essential role of Cdc45 in genomic duplication. The cell cycle division protein Cdc45 is required for genome duplication in eukaryotes. Here, the authors determine the crystal structure of human Cdc45 and combine it with functional data to improve our understanding of its role in DNA replication.