Cyclin A-Cdk1 regulates the origin firing program in mammalian cells
Cyclin A-Cdk1 regulates the origin firing program in mammalian cells
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DOI：
10.1073/pnas.0809350106
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发表时间：
2009-03-03
影响因子：
11.1
通讯作者：
Nakanishi, Makoto
中科院分区：
文献类型：
--
作者：
Katsuno, Yuko;Suzuki, Ayumi;Nakanishi, Makoto
体细胞哺乳动物细胞具有完善的S期程序，其中基因组的特定区域在精确的时间复制。ATR-Chk 1通路在这些程序中起着核心作用，但Chk 1如何调节起源放电的机制仍然未知。我们在这里展示了细胞周期蛋白A2-Cdk 1在调节晚期起源放电中的重要作用。细胞周期蛋白A2-Cdk 1在S期开始时几乎没有活性，但在未扰动条件下，在S期中晚期有明显活性。Chk 1缺失导致Cdc 25 A表达增加，随后细胞周期蛋白A2-Cdk 1过度活化，以及早期S期的异常复制。因此，异位表达的细胞周期蛋白A2-Cdk 1AF（组成型活性突变体）融合结构导致异常的起点射击，导致过早出现的DNA复制在早期S期的晚起源。有趣的是，失活的Cdk 1在温度敏感的Cdk 1突变体细胞系（FT 210）导致在一个延长的S期和低效的激活晚起源射击，即使在晚S期。因此，我们的研究结果表明，细胞周期蛋白A2-Cdk 1是一个关键的调节S期程序。
Somatic mammalian cells possess well-established S-phase programs with specific regions of the genome replicated at precise times. The ATR-Chk1 pathway plays a central role in these programs, but the mechanism for how Chk1 regulates origin firing remains unknown. We demonstrate here the essential role of cyclin A2-Cdk1 in the regulation of late origin firing. Activity of cyclin A2-Cdk1 was hardly detected at the onset of S phase, but it was obvious at middle to late S phase under unperturbed condition. Chk1 depletion resulted in increased expression of Cdc25A, subsequent hyperactivation of cyclin A2-Cdk1, and abnormal replication at early S phase. Hence, the ectopic expression of cyclin A2-Cdk1AF (constitutively active mutant) fusion constructs resulted in abnormal origin firing, causing the premature appearance of DNA replication at late origins at early S phase. Intriguingly, inactivation of Cdk1 in temperature-sensitive Cdk1 mutant cell lines (FT210) resulted in a prolonged S phase and inefficient activation of late origin firing even at late S phase. Our results thus suggest that cyclin A2-Cdk1 is a key regulator of S-phase programs.