High levels of Cdc7 and Dbf4 proteins can arrest cell-cycle progression
High levels of Cdc7 and Dbf4 proteins can arrest cell-cycle progression
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DOI：
10.1016/j.ejcb.2005.09.016
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发表时间：
2005-12-01
影响因子：
6.6
通讯作者：
Lee, H
中科院分区：
文献类型：
--
作者：
Guo, BQ;Romero, J;Lee, H
CDC7-Dbf4丝氨酸/苏氨酸激酶是启动DNA复制所必需的。以往的研究发现，在分裂酵母中过表达某些复制蛋白，如CDC6和CDT1，导致在没有有丝分裂的情况下进行多轮DNA复制。由于这种现象依赖于野生型Cdc7/Hsk1的存在，我们推测高水平的Cdc7和/或Dbf4也可以引起多轮DNA复制，或者可能有助于进入S期。为了验证这一假设，我们在CHO细胞中瞬时过表达仓鼠CDC7和/或Dbf4。荧光显微镜对单个细胞的直接观察和对细胞群体的流式细胞仪分析表明，CDC7和/或Dbf4的过表达不会导致多轮DNA复制或促进进入S期。相反，适度增加的Dbf4水平，而不是CDC7水平，会导致G2/M细胞周期停滞。这种G2/M停滞与CDc2/CDK1在Tyr-15处的过度磷酸化相吻合，从而增加了高水平的Dbf4可能激活G2/M细胞周期检查点的可能性。进一步增加CDC7和/或Dbf4 2-4倍，可使已进入S期的细胞停滞于G1期，并明显延缓S期细胞的进展。(C)2005年爱思唯尔股份有限公司。版权所有。
Cdc7-Dbf4 serine/threonine kinase is essential for initiation of DNA replication. It was previously found that overexpression of certain replication proteins such as Cdc6 and Cdt1 in fission yeast resulted in multiple rounds of DNA replication in the absence of mitosis. Since this phenomenon is dependent upon the presence of wild-type Cdc7/Hsk1, we hypothesized that high levels of Cdc7 and/or Dbf4 could also cause multiple rounds of DNA replication, or could facilitate entry into S phase. To test this hypothesis, we transiently overexpressed hamster Cdc7, Dbf4 or both in CHO cells. Direct observations of individual cells by fluorescence microscopy and flow cytometric analysis on cell populations suggest that overexpression of Cdc7 and/or Dbf4 does not result in multiple rounds of DNA replication or facilitating entry into S phase. In contrast, moderately increased levels of Dbf4, but not Cdc7, cause cell-cycle arrest in G2/M. This G2/M arrest coincides with hyperphosphorylation of Cdc2/Cdk1 at Tyr-15, raising the possibility that high levels of Dbf4 may activate a G2/M cell-cycle checkpoint. Further increase in Cdc7 and/or Dbf4 by 2-4 fold can arrest cells in G1 and significantly slow down S-phase progression for the cells already in S phase. (c) 2005 Elsevier GmbH. All rights reserved.