Gambus Agnieszka, van Deursen Frederick, Polychronopoulos Dimitrios, Foltman Magdalena, Jones Richard C, Edmondson Ricky D, Calzada Arturo, Labib Karim
Cancer Research UK, Paterson Institute for Cancer Research, University of Manchester, Manchester, UK.
EMBO J. 2009 Oct 7;28(19):2992-3004. doi: 10.1038/emboj.2009.226. Epub 2009 Aug 6.
The eukaryotic replisome is a crucial determinant of genome stability, but its structure is still poorly understood. We found previously that many regulatory proteins assemble around the MCM2-7 helicase at yeast replication forks to form the replisome progression complex (RPC), which might link MCM2-7 to other replisome components. Here, we show that the RPC associates with DNA polymerase alpha that primes each Okazaki fragment during lagging strand synthesis. Our data indicate that a complex of the GINS and Ctf4 components of the RPC is crucial to couple MCM2-7 to DNA polymerase alpha. Others have found recently that the Mrc1 subunit of RPCs binds DNA polymerase epsilon, which synthesises the leading strand at DNA replication forks. We show that cells lacking both Ctf4 and Mrc1 experience chronic activation of the DNA damage checkpoint during chromosome replication and do not complete the cell cycle. These findings indicate that coupling MCM2-7 to replicative polymerases is an important feature of the regulation of chromosome replication in eukaryotes, and highlight a key role for Ctf4 in this process.
真核生物复制体是基因组稳定性的关键决定因素，但其结构仍知之甚少。我们之前发现，许多调控蛋白在酵母复制叉处围绕MCM2 - 7解旋酶组装，形成复制体进展复合体（RPC），该复合体可能将MCM2 - 7与其他复制体组分连接起来。在此，我们表明RPC与DNA聚合酶α相关联，DNA聚合酶α在滞后链合成过程中引发每个冈崎片段。我们的数据表明，RPC的GINS和Ctf4组分的复合体对于将MCM2 - 7与DNA聚合酶α偶联至关重要。其他人最近发现，RPC的Mrc1亚基结合DNA聚合酶ε，后者在DNA复制叉处合成前导链。我们表明，同时缺乏Ctf4和Mrc1的细胞在染色体复制过程中会经历DNA损伤检查点的慢性激活，并且无法完成细胞周期。这些发现表明，将MCM2 - 7与复制性聚合酶偶联是真核生物染色体复制调控的一个重要特征，并突出了Ctf4在此过程中的关键作用。
