Rickert P, Seghezzi W, Shanahan F, Cho H, Lees E
DNAX Research Institutte of Molecular and Cellular Biology, Palo Alto, California 94304, USA.
Oncogene. 1996 Jun 20;12(12):2631-40.
A number of cyclin/kinase complexes have been identified in mammalian cells that are essential for controlled cell proliferation. Cyclin C was isolated by virtue of its ability to rescue the triple CLN mutation in yeast; however, until now its function has remained unclear. Cyclin C associates with a novel cyclin dependent kinase, CDK8, and we demonstrate that this complex is associated with kinase activity towards the carboxy-terminal domain (CTD) of RNA polymerase II. We have identified at least two distinct cyclin C/CDK8 containing complexes within the cell, a larger complex over 500 kD in size, that also contains the largest subunit of RNA polymerase II, and a smaller 170 kD species. Both of these cyclin C complexes retain potent CTD kinase activity. We further demonstrate that the cyclin C/CDK8 complex associates with the large subunit of RNA polymerase II in vivo, implicating a potential role for cyclin C/CDK8 in regulating its activities.
在哺乳动物细胞中已鉴定出多种细胞周期蛋白/激酶复合物，它们对于细胞增殖的调控至关重要。细胞周期蛋白C因其能够挽救酵母中的三重CLN突变而被分离出来；然而，直到现在其功能仍不清楚。细胞周期蛋白C与一种新型细胞周期蛋白依赖性激酶CDK8相关联，并且我们证明这种复合物与针对RNA聚合酶II羧基末端结构域（CTD）的激酶活性有关。我们在细胞内鉴定出至少两种不同的含细胞周期蛋白C/CDK8的复合物，一种较大的复合物，大小超过500 kD，还包含RNA聚合酶II的最大亚基，以及一种较小的170 kD的复合物。这两种细胞周期蛋白C复合物都保留了强大的CTD激酶活性。我们进一步证明，细胞周期蛋白C/CDK8复合物在体内与RNA聚合酶II的大亚基相关联，这暗示细胞周期蛋白C/CDK8在调节其活性方面可能发挥作用。
