Human TopBP1 ensures genome integrity during normal S phase
Human TopBP1 ensures genome integrity during normal S phase
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DOI：
10.1128/mcb.25.24.10907-10915.2005
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发表时间：
2005-12-01
影响因子：
5.3
通讯作者：
Chen, JJ
中科院分区：
文献类型：
--
作者：
Kim, JE;McAvoy, SA;Chen, JJ
细胞周期检查点对于维持基因组的完整性是必不可少的。人拓扑异构酶H结合蛋白1(TopBP1)与芽生酵母Dpb11、裂解酵母Rad4/Cut5和非洲爪哇Cut5序列相似，都是DNA复制和细胞周期检查点所必需的。事实上，我们已经证明，在羟基脲处理和电离辐射之后，人TopBP1参与了复制检查点和DNA损伤检查点的激活。在本研究中，我们利用小干扰RNA研究了TopBP1在S期的生理功能。在没有外源DNA损伤的情况下，TopBP1被招募来复制染色质。然而，TopBP1似乎并不是DNA复制所必需的。TopBP1缺失的细胞增加了H2AX的磷酸化和ATM-Chk2的激活，这表明在没有TopBP1的情况下DNA双链断裂积累。这会导致脆弱部位形成缺口和断裂，4N积累，细胞分裂异常。我们认为TopBP1的细胞功能是监控正在进行的DNA复制。通过确保适当的DNA复制，TopBP1在维持正常S期和随后的遗传毒性胁迫期间的基因组稳定性方面发挥了关键作用。
Cell cycle checkpoints are essential for maintaining genomic integrity. Human topoisomerase H binding protein 1 (TopBP1) shares sequence similarity with budding yeast Dpb11, fission yeast Rad4/Cut5, and Xenopus Cut5, all of which are required for DNA replication and cell cycle checkpoints. Indeed, we have shown that human TopBP1 participates in the activation of replication checkpoint and DNA damage checkpoints, following hydroxyurea treatment and ionizing radiation. In this study, we address the physiological function of TopBP1 in S phase by using small interfering RNA. In the absence of exogenous DNA damage, TopBP1 is recruited to replicating chromatin. However, TopBP1 does not appear to be essential for DNA replication. TopBP1-deficient cells have increased H2AX phosphorylation and ATM-Chk 2 activation, suggesting the accumulation of DNA double-strand breaks in the absence of TopBP1. This leads to formation of gaps and breaks at fragile sites, 4N accumulation, and aberrant cell division. We propose that the cellular function of TopBP1 is to monitor ongoing DNA replication. By ensuring proper DNA replication, TopBP1 plays a critical role in the maintenance of genomic stability during normal S phase as well as following genotoxic stress.