Cell cycle control of Cdc7p kinase activity through regulation of Dbf4p stability.
Cell cycle control of Cdc7p kinase activity through regulation of Dbf4p stability.
复制标题
通过调节 Dbf4p 稳定性来控制 Cdc7p 激酶活性的细胞周期。
DOI：
10.1128/mcb.19.7.4888
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发表时间：
1999
影响因子：
5.3
通讯作者：
Li,JJ
中科院分区：
文献类型：
--
作者：
Oshiro,G;Owens,JC;Shellman,Y;Sclafani,RA;Li,JJ
在酿酒酵母中，异构体激酶复合体Cdc7p-Dbf4p在复制起始处起着关键作用，触发了S时期的DNA复制。我们已经用一个可能的生理靶标Mcm2p作为底物，检测了内源性水平的CDC7P激酶的活性。利用该方法，我们证实了CDC7P激酶活性在细胞周期中波动；在G1期活性较低，随着细胞进入S期而上升，并保持较高水平，直到细胞完成有丝分裂。这些激酶活性的变化不能用催化亚单位CDC7P水平的变化来解释，因为这些水平在细胞周期中是恒定的。然而，激酶活性的波动确实与调节亚单位Dbf4p的水平有关。Dbf4p水平的调节可以部分归因于G1细胞中蛋白质降解的增加。这种G1期的不稳定性是依赖于cdc16的，表明后期促进复合体在Dbf4p的周转中发挥了作用。在G1期过表达Dbf4p可以部分克服这种升高的周转，并导致CDC7p激酶活性的增加。因此，通过控制Dbf4p的降解来调节Dbf4p的水平，在细胞周期中调节CDC7p的活性具有重要的作用。
InSaccharomyces cerevisiae, the heteromeric kinase complex Cdc7p-Dbf4p plays a pivotal role at replication origins in triggering the initiation of DNA replication during the S phase. We have assayed the kinase activity of endogenous levels of Cdc7p kinase by using a likely physiological target, Mcm2p, as a substrate. Using this assay, we have confirmed that Cdc7p kinase activity fluctuates during the cell cycle; it is low in the G1phase, rises as cells enter the S phase, and remains high until cells complete mitosis. These changes in kinase activity cannot be accounted for by changes in the levels of the catalytic subunit Cdc7p, as these levels are constant during the cell cycle. However, the fluctuations in kinase activity do correlate with levels of the regulatory subunit Dbf4p. The regulation of Dbf4p levels can be attributed in part to increased degradation of the protein in G1cells. This G1-phase instability iscdc16dependent, suggesting a role of the anaphase-promoting complex in the turnover of Dbf4p. Overexpression of Dbf4p in the G1phase can partially overcome this elevated turnover and lead to an increase in Cdc7p kinase activity. Thus, the regulation of Dbf4p levels through the control of Dbf4p degradation has an important role in the regulation of Cdc7p kinase activity during the cell cycle.