A NOVEL CYCLIN ASSOCIATES WITH MO15/CDK7 TO FORM THE CDK-ACTIVATING KINASE
A NOVEL CYCLIN ASSOCIATES WITH MO15/CDK7 TO FORM THE CDK-ACTIVATING KINASE
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DOI：
10.1016/0092-8674(94)90535-5
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发表时间：
1994-08-26
期刊：
影响因子：
64.5
通讯作者：
MORGAN, DO
中科院分区：
文献类型：
--
作者：
FISHER, RP;MORGAN, DO
CDK活化激酶（CAK）的磷酸化是细胞周期蛋白依赖性激酶活化的必要步骤。我们已经从哺乳动物细胞中纯化了CAK;该酶包括42和37 kDa的两种主要多肽。蛋白质测序表明，42 kDa的亚基是哺乳动物的同源物MO 15，蛋白激酶已知是在两栖动物和棘皮动物的CAK的一个组成部分。克隆编码37 kDa亚基的cDNA鉴定其为一种新的细胞周期蛋白（细胞周期蛋白H）。我们在体外用MO 15催化亚基和细胞周期蛋白H重建了CAK，证明MO 15是一种细胞周期蛋白依赖性激酶（CDK 7）。与其他CDK一样，MO 15/CDK 7含有完全活性所需的保守苏氨酸;该残基的突变严重降低CAK活性。CAK全酶激活CDK 2和CDC 2与各种细胞周期蛋白的复合物，并且在细胞周期蛋白不存在的情况下也磷酸化CDK 2，但不磷酸化CDC 2。因此，CAK是一种CDK-细胞周期蛋白复合物，参与多种细胞周期转换的控制。
Phosphorylation by the CDK-activating kinase (CAK) is a required step in the activation of cyclin-dependent kinases. We have purified CAK from mammalian cells; the enzyme comprises two major polypeptides of 42 and 37 kDa. Protein sequencing indicates that the 42 kDa subunit is the mammalian homolog of MO15, a protein kinase known to be a component of CAK in amphibians and echinoderms. Cloning of a cDNA encoding the 37 kDa subunit identifies it as a novel cyclin (cyclin H). We have reconstituted CAK in vitro with the MO15 catalytic subunit and cyclin H, demonstrating that MO15 is a cyclin-dependent kinase (CDK7). Like other CDKs, MO15/CDK7 contains a conserved threonine required for full activity; mutation of this residue severely reduces CAK activity. The CAK holoenzyme activates complexes of CDK2 and CDC2 with various cyclins and also phosphorylates CDK2, but not CDC2, in the absence of cyclin. Thus, CAK is a CDK-cyclin complex implicated in the control of multiple cell cycle transitions.