Cdc2 regulation for the meiotic transition from M phase to M phase

为了研究减数分裂周期中细胞周期从M期到M期转变的调控机制，已经开发了执行M/M转变的爪蟾卵母细胞提取物。使用减数分裂提取物，我们发现低水平的Cdc 2活性保持在减数分裂I（MI）的出口处，由于细胞周期蛋白B的不完全降解。剩余Cdc 2活性的失活诱导细胞进入S期和酪氨酸-β受体结合。定量分析表明，在MI出口处存在相当数量的Weel，并且在此期间Cdc 2抑制磷酸化。Cdc 2对Weel的优势抑制。一致地，向提取物中添加超过临界量的Weel诱导Cdc 2抑制性磷酸化，将M/M转变为M/S/M转变。因此，Cdc 2活性保留在MI出口抑制进入S期在减数分裂M/M过渡期。

To investigate the regulatory mechanisms for the cell cycle transition from M phase to M phase in meiotic cycles, a Xenopus oocyte extract that performs the M/M transition has been developed. Using the meiotic extract, we found that a low level of Cdc2 activity remained at the exit of meiosis I (MI), due to incomplete degradation of cyclin B.The inactivation of the residual Cdc2 activity induced both entry into S phase and tyrosine-phosphorylation on Cdc2 after MI.Quantitative analysis demonstrated that a considerable amount of Weel was present at the MI exit and Cdc2 inhibitory phosphorylation during this period was suppressed by the dominance of Cdc2 over Weel. Consistently, the addition of more than a critical amount of Weel to the extract induced Cdc2 inhibitory phosphorylation, changing the M/M transition into an M/S/M transition. Thus, the Cdc2 activity remaining at the MI exit is required for suppressing entry into S phase during the meiotic M/M transition period.