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首页> 外文期刊>Molecular and Cellular Biology >Role for Cdk1 (Cdc2)/Cyclin A in Preventing the Mammalian Origin Recognition Complex's Largest Subunit (Orc1) from Binding to Chromatin during Mitosis
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Role for Cdk1 (Cdc2)/Cyclin A in Preventing the Mammalian Origin Recognition Complex's Largest Subunit (Orc1) from Binding to Chromatin during Mitosis

机译：Cdk1（Cdc2）/ Cyclin A在防止哺乳动物起源识别复合体的最大亚基（Orc1）在有丝分裂过程中与染色质结合中的作用

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The eukaryotic origin recognition complex (ORC) selects the genomic sites where prereplication complexes are assembled and DNA replication begins. In proliferating mammalian cells, ORC activity appears to be regulated by reducing the affinity of the Orc1 subunit for chromatin during S phase and then preventing reformation of a stable ORC-chromatin complex until mitosis is completed and a nuclear membrane is assembled. Here we show that part of the mechanism by which this is accomplished is the selective association of Orc1 with Cdk1 (Cdc2)/cyclin A during the G2/M phase of cell division. This association accounted for the appearance in M-phase cells of hyperphosphorylated Orc1 that was subsequently dephosphorylated during the M-to-G1 transition. Moreover, inhibition of Cdk activity in metaphase cells resulted in rapid binding of Orc1 to chromatin. However, chromatin binding was not mediated through increased affinity of Orc1 for Orc2, suggesting that additional events are involved in the assembly of functional ORC-chromatin sites. These results reveal that the same cyclin-dependent protein kinase that initiates mitosis in mammalian cells also concomitantly inhibits assembly of functional ORC-chromatin sites.
机译：真核生物起源识别复合物（ORC）选择组装复制前复合物并开始DNA复制的基因组位点。在增殖的哺乳动物细胞中，似乎可以通过在S期降低Orc1亚基对染色质的亲和力，然后阻止稳定的ORC-染色质复合物再形成直至有丝分裂完成并组装核膜来调节ORC活性。在这里，我们证明了完成此过程的部分机制是在细胞分裂的G 2 / M阶段Orc1与Cdk1（Cdc2）/ cyclin A的选择性结合。这种联系解释了高磷酸化的Orc1在M期细胞中的出现，随后在M到G 1 的转变过程中被去磷酸化。此外，在中期细胞中Cdk活性的抑制导致Orc1与染色质的快速结合。但是，染色质结合不是通过增加Orc1对Orc2的亲和力来介导的，这表明功能性ORC染色质位点的组装还涉及其他事件。这些结果表明，在哺乳动物细胞中引发有丝分裂的细胞周期蛋白依赖性蛋白激酶也能同时抑制功能性ORC染色质位点的组装。

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