Cdc7-Dbf4 phosphorylates MCM proteins via a docking site-mediated mechanism to promote S phase progression
Cdc7-Dbf4 phosphorylates MCM proteins via a docking site-mediated mechanism to promote S phase progression
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DOI：
10.1016/j.molcel.2006.07.033
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发表时间：
2006-10-06
期刊：
影响因子：
16
通讯作者：
Stillman, Bruce
中科院分区：
文献类型：
--
作者：
Sheu, Yi-Jun;Stillman, Bruce
DNA复制的起点在G1中是通过招募微小染色体维持(MCM)蛋白形成复制前复合体(Pre-RC)而获得许可的。在每个来源的DNA合成开始之前，都会形成一个包含Cdc45和其他蛋白质的预引发复合体(PreIC)。我们报道了在S时相，CDC7-Dbf4蛋白激酶(DDK)促进了染色质上稳定的CDC45-MCM复合体的组装。在这个复合体中，Mcm4过度磷酸化。用纯化的DDK和Mcm4进行的体外研究表明，Mcm4的N末端发生了过度磷酸化。然而，DDK底物的特异性是由相邻的DDK-对接结构域(DDD)赋予的，足以促进顺式人工磷受体的有效磷酸化。遗传学证据表明，DDK对Mcm4的磷酸化对于及时的S期进展和过量生产CDC45时的细胞存活是重要的。我们建议DDK在许可的来源对接并磷酸化MCM蛋白，以促进前IC的正确组装。
Origins of DNA replication are licensed in G1 by recruiting the minichromosome maintenance (MCM) proteins to form a prereplicative complex (pre-RC). Prior to initiation of DNA synthesis from each origin, a preinitiation complex (pre-IC) containing Cdc45 and other proteins is formed. We report that Cdc7-Dbf4 protein kinase (DDK) promotes assembly of a stable Cdc45-MCM complex exclusively on chromatin in S phase. In this complex, Mcm4 is hyperphosphorylated. Studies in vitro using purified DDK and Mcm4 demonstrate that hyperphosphorylation occurs at the Mcm4 N terminus. However, the DDK substrate specificity is conferred by an adjacent DDK-docking domain (DDD), sufficient for facilitating efficient phosphorylation of artificial phosphoacceptors in cis. Genetic evidence suggests that phosphorylation of Mcm4 by DDK is important for timely S phase progression and for cell viability upon overproduction of Cdc45. We suggest that DDK docks on and phosphorylates MCM proteins at licensed origins to promote proper assembly of pre-IC.