Dormant origins licensed by excess Mcm2-7 are required for human cells to survive replicative stress.
Dormant origins licensed by excess Mcm2-7 are required for human cells to survive replicative stress.
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DOI：
10.1101/gad.457807
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发表时间：
2007-12-15
影响因子：
10.5
通讯作者：
Blow, J Julian
中科院分区：
文献类型：
--
作者：
Ge, Xin Quan;Jackson, Dean A;Blow, J Julian
在有丝分裂晚期和G1早期，Mcm 2 -7复合物被加载到DNA上，以许可复制起点用于即将到来的S期。然而，装载的Mcm 2 -7的量明显超过通常使用的原点的数量。我们在这里表明，在人类细胞中，过量的染色质结合Mcm 2 -7许可休眠的复制起点，在正常的DNA复制过程中不火，部分原因是检查点活动。尽管激活了S期检查点，但如果复制叉进展被抑制，则在活性复制子簇内激活了Dorpus起源。在通过RNAi降低人类细胞中染色质结合的Mcm 2 -7水平后，响应于复制应激，休眠起源的使用被抑制。虽然细胞与降低染色质结合Mcm 2 -7复制在正常的速度，当挑战与复制抑制剂，他们有显着降低的DNA合成率和降低的活力。这些结果表明，使用休眠的起源许可过量Mcm 2 -7是一个新的和生理上重要的机制，细胞利用复制应激条件下维持DNA复制速率。我们建议，检查点激酶活性可以优先抑制启动内不活跃的复制子集群，从而指导新的启动事件对活跃的集群正在经历复制问题。
In late mitosis and early G1, Mcm2-7 complexes are loaded onto DNA to license replication origins for use in the upcoming S phase. However, the amount of Mcm2-7 loaded is in significant excess over the number of origins normally used. We show here that in human cells, excess chromatin-bound Mcm2-7 license dormant replication origins that do not fire during normal DNA replication, in part due to checkpoint activity. Dormant origins were activated within active replicon clusters if replication fork progression was inhibited, despite the activation of S phase checkpoints. After lowering levels of chromatin-bound Mcm2-7 levels in human cells by RNAi, the use of dormant origins was suppressed in response to replicative stress. Although cells with lowered chromatin-bound Mcm2-7 replicated at normal rates, when challenged with replication inhibitors they had dramatically reduced rates of DNA synthesis and reduced viability. These results suggest that the use of dormant origins licensed by excess Mcm2-7 is a new and physiologically important mechanism that cells utilize to maintain DNA replication rates under conditions of replicative stress. We propose that checkpoint kinase activity can preferentially suppresses initiation within inactive replicon clusters, thereby directing new initiation events towards active clusters that are experiencing replication problems.