Yoshida N, Yamashita M
Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo, Japan.
Dev Growth Differ. 2000 Jun;42(3):285-94. doi: 10.1046/j.1440-169x.2000.00506.x.
Cdk2 kinase activity increases during oocyte maturation but neither cyclin A nor B is associated with Cdk2 in mature oocytes in goldfish. As a potential Cdk2 partner in meiosis, a cyclin E homolog was isolated from a goldfish oocyte cDNA library. A monoclonal antibody was raised against bacterially produced full-length goldfish cyclin E. Both cyclin E and Cdk2 were already present in immature oocytes and their protein levels did not change remarkably during oocyte maturation. Cyclin E formed a complex mainly with Cdk2 just at the time of germinal vesicle breakdown (GVBD) in association with the increase in Cdk2 kinase activity, although a fraction of cyclin E bound to Cdk(s) other than Cdk2 and Cdc2. Ectopic activation of cyclin E/Cdk2 by the injection of cyclin E messenger RNA (mRNA) into immature oocytes did not induce maturation-promoting factor (MPF) activation and GVBD. Furthermore, inhibition of cyclin E/Cdk2 kinase activity by the injection of p21SDI1 into the oocytes treated with 17alpha,20beta-dihydroxy-4-pregnen-3-one had no effect on MPF activation and GVBD. These results indicate that cyclin E/Cdk2 kinase activity is insufficient and unnecessary for initiating goldfish oocyte maturation.
在金鱼卵母细胞成熟过程中，Cdk2激酶活性增加，但在成熟卵母细胞中，细胞周期蛋白A和B均不与Cdk2相关联。作为减数分裂中潜在的Cdk2伴侣，从金鱼卵母细胞cDNA文库中分离出一种细胞周期蛋白E同源物。制备了针对细菌产生的全长金鱼细胞周期蛋白E的单克隆抗体。细胞周期蛋白E和Cdk2在未成熟卵母细胞中就已存在，并且它们的蛋白质水平在卵母细胞成熟过程中没有明显变化。就在生发泡破裂（GVBD）时，随着Cdk2激酶活性的增加，细胞周期蛋白E主要与Cdk2形成复合物，尽管一部分细胞周期蛋白E与Cdk2和Cdc2以外的其他Cdk结合。通过将细胞周期蛋白E信使核糖核酸（mRNA）注射到未成熟卵母细胞中异位激活细胞周期蛋白E/Cdk2，并未诱导成熟促进因子（MPF）激活和GVBD。此外，向用17α,20β-二羟基-4-孕烯-3-酮处理的卵母细胞中注射p21SDI1来抑制细胞周期蛋白E/Cdk2激酶活性，对MPF激活和GVBD没有影响。这些结果表明，细胞周期蛋白E/Cdk2激酶活性对于启动金鱼卵母细胞成熟既不充分也不必要。
