Marraccino R L, Firpo E J, Roberts J M
Department of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington 98104.
Mol Biol Cell. 1992 Apr;3(4):389-401. doi: 10.1091/mbc.3.4.389.
Using a protocol for selecting cells on the basis of both size and age (with respect to the preceding mitosis), we isolated highly synchronous human G1 cells. With this procedure, we demonstrated that the p34 CDC2 kinase was activated at the start of S phase. Cyclin A synthesis began at the same time, and activation of the p34 CDC2 kinase at the start of S phase was, at least in part, due to its association with cyclin A. Furthermore, cells synchronized in late G1 by exposure to the drug mimosine contain active cyclin A/p34 CDC2 kinase, indicating that p34 CDC2 activation can occur before DNA synthesis begins. Thus, the cyclin A/CDC2 complex, which previously has been shown to be sufficient to start SV40 DNA synthesis in vitro, assembles and is activated at the start of S phase in vivo.
我们使用一种基于大小和年龄（相对于前一次有丝分裂）来选择细胞的方案，分离出了高度同步化的人G1期细胞。通过这个程序，我们证明了p34 CDC2激酶在S期开始时被激活。细胞周期蛋白A的合成同时开始，并且S期开始时p34 CDC2激酶的激活至少部分是由于它与细胞周期蛋白A的结合。此外，通过暴露于含羞草碱药物而在G1晚期同步化的细胞含有活性细胞周期蛋白A/p34 CDC2激酶，这表明p34 CDC2的激活可以在DNA合成开始之前发生。因此，先前已证明足以在体外启动SV40 DNA合成的细胞周期蛋白A/CDC2复合物，在体内S期开始时组装并被激活。
