Tanaka Toyomi, Yamashita Masakane
Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo 060, Japan.
Dev Growth Differ. 1995 Aug;37(4):387-393. doi: 10.1046/j.1440-169X.1995.t01-3-00005.x.
Maturation-promoting factor (MPF), a final trigger for initiating oocyte maturation, is activated in the oocyte cytoplasm, in response to maturation-inducing hormone (MIH) secreted from follicle cells surrounding the oocyte. MPF consists of cdc2 and cyclin B. We investigated the state of cdc2 and cyclin B in immature and mature oocytes of fishes (carp, catfish and lamprey) and amphibians (Xenopus, frog [Rana] and toad [Bufo]) using monoclonal antibodies raised against mouse cdc2, which also recognize fish and amphibian cdc2, and monoclonal antibodies against goldfish cyclin B1 and polyclonal antibodies against Xenopus cyclins B1 and B2. Anti-cdc2 and anti-cyclin B immunoblotting of oocyte extracts fractionated by gel filtration chromatography showed that immature oocytes from all of these species with the exception of Xenopus contained only monomeric cdc2. Cyclin B-bound inactive cdc2 (pre-MPF) was present only in immature Xenopus oocytes. Cdc2-cyclin B complex was, however, found in mature oocytes from all the species examined. After the oocyte is induced to mature by MIH, cdc2 should therefore bind to cyclin B in all of these species, except Xenopus. These results suggest that the complex formation of cdc2 and cyclin B in response to MIH stimulation at the oocyte surface is a critical step for initiating oocyte maturation in fishes and amphibians, with the exception of Xenopus, in which pre-MPF already exists in immature oocytes and only its chemical modification is required for MPF activation.
成熟促进因子（MPF）是启动卵母细胞成熟的最终触发因素，它在卵母细胞细胞质中被激活，以响应卵母细胞周围卵泡细胞分泌的成熟诱导激素（MIH）。MPF由细胞周期蛋白依赖性激酶2（cdc2）和细胞周期蛋白B组成。我们使用针对小鼠cdc2的单克隆抗体（该抗体也可识别鱼类和两栖类动物的cdc2）、针对金鱼细胞周期蛋白B1的单克隆抗体以及针对非洲爪蟾细胞周期蛋白B1和B2的多克隆抗体，研究了鱼类（鲤鱼、鲶鱼和七鳃鳗）和两栖类动物（非洲爪蟾、蛙[林蛙属]和蟾蜍[蟾蜍属]）未成熟和成熟卵母细胞中cdc2和细胞周期蛋白B的状态。通过凝胶过滤色谱法分离的卵母细胞提取物的抗cdc2和抗细胞周期蛋白B免疫印迹显示，除非洲爪蟾外，所有这些物种的未成熟卵母细胞仅含有单体cdc2。与细胞周期蛋白B结合的无活性cdc（前MPF）仅存在于未成熟的非洲爪蟾卵母细胞中。然而，在所检测的所有物种的成熟卵母细胞中都发现了cdc2 - 细胞周期蛋白B复合物。因此，在MIH诱导卵母细胞成熟后，除非洲爪蟾外，所有这些物种中的cdc2都应与细胞周期蛋白B结合。这些结果表明，在卵母细胞表面对MIH刺激做出反应时，cdc2和细胞周期蛋白B的复合物形成是鱼类和两栖类动物（非洲爪蟾除外）启动卵母细胞成熟的关键步骤，在非洲爪蟾中，前MPF已存在于未成熟卵母细胞中，MPF激活仅需要其化学修饰。
