Human Geminin promotes pre-RC formation and DNA replication by stabilizing CDT1 in mitosis
Human Geminin promotes pre-RC formation and DNA replication by stabilizing CDT1 in mitosis
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DOI：
10.1038/sj.emboj.7600314
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发表时间：
2004-08-04
期刊：
影响因子：
11.4
通讯作者：
Helin, K
中科院分区：
文献类型：
--
作者：
Ballabeni, A;Melixetian, M;Helin, K
Geminin是一种不稳定的DNA复制抑制剂，负调控许可因子CDT 1，并抑制爪蟾卵提取物中复制前复合物（pre-RC）的形成。在这里，我们描述一个新的功能Geminin。我们证明，人类Geminin保护CDT 1从蛋白酶体介导的降解抑制其泛素化。特别是，Geminin确保CDT 1在S期的基础水平及其在有丝分裂期间的积累。因此，在M期抑制Geminin的合成会导致在随后的细胞周期中前RC形成和DNA复制的损害。此外，我们发现，在有丝分裂过程中抑制CDK 1，而不是Geminin耗尽，足以过早形成前RC，表明CDK活性是人类细胞中许可的主要有丝分裂抑制剂。结合我们实验室的最新数据，我们的结果表明，Geminin是人类细胞中前RC形成的负调节剂和正调节剂，在允许CDT 1在G2-M中积累和防止S-G2中起源的再授权方面发挥积极作用。
Geminin is an unstable inhibitor of DNA replication that negatively regulates the licensing factor CDT1 and inhibits pre-replicative complex (pre-RC) formation in Xenopus egg extracts. Here we describe a novel function of Geminin. We demonstrate that human Geminin protects CDT1 from proteasome-mediated degradation by inhibiting its ubiquitination. In particular, Geminin ensures basal levels of CDT1 during S phase and its accumulation during mitosis. Consistently, inhibition of Geminin synthesis during M phase leads to impairment of pre-RC formation and DNA replication during the following cell cycle. Moreover, we show that inhibition of CDK1 during mitosis, and not Geminin depletion, is sufficient for premature formation of pre-RCs, indicating that CDK activity is the major mitotic inhibitor of licensing in human cells. Taken together with recent data from our laboratory, our results demonstrate that Geminin is both a negative and positive regulator of pre-RC formation in human cells, playing a positive role in allowing CDT1 accumulation in G2-M, and preventing relicensing of origins in S-G2.