CELL CYCLE CONTROL IN EARLY DEVELOPMENT

在本研究项目中，我们利用两栖动物爪蟾系统获得了以下结果。(1)与普遍观点相反，核物质对卵母细胞成熟过程中MPF的激活至关重要。(2)卵母细胞成熟过程中，双极纺锤体的形成需要细胞周期蛋白B2，而不需要细胞周期蛋白B1。(3)检查点激酶Chk1是卵母细胞G2阻滞所必需的，在其c端含有一个自身抑制区。(4) Wee1激酶在减数分裂I卵母细胞中缺失，这种缺失对于进入减数分裂II至关重要。(5)存在于3'UTR中的AUUUA基序对受精时Mos mRNA的翻译阻滞至关重要。(6) Nek2激酶对卵裂胚中心体的形成和维持至关重要。(7)两种不同的Weel亚型，母体Wee1A和合子Wee1B，存在于早期胚胎中，并参与细胞周期的母体/合子过渡。(8) Chk1激酶在中囊胚转变的生理复制检查点瞬时激活，并直接靶向Cdc25A在此转变中降解。

In this research project, we obtained the-following results using the amphibian Xenopus system. (1) Contrary to the generally accepted view, nuclear material is essential for the activation of MPF during oocyte maturation. (2) Cyclin B2, but not cyclin B1, is required for bipolar spindle formation during oocyte maturation. (3) The checkpoint kinase Chk1 is required for G2 arrest of oocytes and contains an autoinhibitory region at its C-terminus. (4) Wee1 kinase is absent in meiosis I oocytes and this lack of Weel is essential for entry into meiosis II. (5) The AUUUA motif present in the 3'UTR is essential for translational arrest of Mos mRNA upon fertilization. (6) Nek2 kinase is essential for the formation and maintenance of centrosomes in cleaving embryos. .(7) Two distinct Weel isoforms, maternal Wee1A and zygotic Wee1B, exist in early embryos and are involved in the maternal/zygotic transition of the cell cycle. (8) Chk1 kinase is activated transiently at a physiological replication checkpoint at the midblastula transition and directly targets Cdc25A for degradation at this transition.