Cyclin B targets p34cdc2 for tyrosine phosphorylation.
Cyclin B targets p34cdc2 for tyrosine phosphorylation.
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DOI：
10.1002/j.1460-2075.1991.tb07674.x
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发表时间：
1991-06
期刊：
影响因子：
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通讯作者：
L. Meijer;L. Azzi;Jean;'. Y.J.Wang
中科院分区：
文献类型：
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作者：
L. Meijer;L. Azzi;Jean;'. Y.J.Wang
一个普遍的细胞内因子，“M期促进因子”（MPF），在所有生物中触发细胞周期的G2/M转变。在G2晚期，它以酪氨酸磷酸化的p34cdc2和未磷酸化的细胞周期蛋白Bcdc13的无活性复合物的形式存在。在M期，其作为显示组蛋白H1激酶（H1K）的活性MPF的激活源于p34cdc2亚基的酪氨酸去磷酸化和细胞周期蛋白Bcdc13亚基的磷酸化。我们使用高度同步的有丝分裂海胆卵作为模型，研究了细胞周期蛋白在该复合体形成和p34cdc2酪氨酸磷酸化中的作用。当细胞离开S期进入G2期时，p34cdc2发生大量酪氨酸磷酸化。这种p34cdc2酪氨酸磷酸化的大爆发不是由p34cdc2浓度的大量增加引起的。它甚至似乎只影响细胞中存在的总p34cdc2的一小部分（抗PSTAIR抗体无法免疫沉淀）。一些观察结果表明，未磷酸化的细胞周期蛋白的积累与p34cdc2酪氨酸磷酸化之间存在极其密切的联系：(1)这两个事件在G2期完全重合；（ii）酪氨酸磷酸化的p34cdc2和细胞周期蛋白都不能被抗PSTAIR抗体免疫沉淀；（iii） aphidicolin处理细胞后，未磷酸化的细胞周期蛋白积累，引发酪氨酸磷酸化p34cdc2的大量积累；（iv）艾美汀抑制细胞周期蛋白合成可抑制p34cdc2酪氨酸磷酸化，但不影响p34cdc2浓度。这些结果表明，在合成过程中，细胞周期蛋白B结合并招募p34cdc2进行酪氨酸磷酸化；这个非活性复合体需要完成DNA复制才能变成完全活跃的MPF。这些结果完全证实了最近在环己亚胺处理的爪蟾卵提取物中添加外源性细胞周期蛋白的体外实验结果。
A universal intracellular factor, the ‘M phase‐promoting factor’ (MPF), triggers the G2/M transition of the cell cycle in all organisms. In late G2, it is present as an inactive complex of tyrosine‐phosphorylated p34cdc2 and unphosphorylated cyclin Bcdc13. In M phase, its activation as an active MPF displaying histone H1 kinase (H1K) originates from the concomitant tyrosine dephosphorylation of the p34cdc2 subunit and the phosphorylation of the cylin Bcdc13 subunit. We have investigated the role of cyclin in the formation of this complex and the tyrosine phosphorylation of p34cdc2, using highly synchronous mitotic sea urchin eggs as a model. As cells leave the S phase and enter the G2 phase, a massive tyrosine phosphorylation of p34cdc2 occurs. This large p34cdc2 tyrosine phosphorylation burst does not arise from a massive increase in p34cdc2 concentration. It even appears to affect only a fraction (non‐immunoprecipitable by anti‐PSTAIR antibodies) of the total p34cdc2 present in the cell. Several observations point to an extremely close association between accumulation of unphosphorylated cyclin and p34cdc2 tyrosine phosphorylation: (i) both events coincide perfectly during the G2 phase; (ii) both tyrosine‐phosphorylated p34cdc2 and cyclin are not immunoprecipitated by anti‐PSTAIR antibodies; (iii) accumulation of unphosphorylated cyclin by aphidicolin treatment of the cells, triggers a dramatic accumulation of tyrosine‐phosphorylated p34cdc2; and (iv) inhibition of cyclin synthesis by emetine inhibits p34cdc2 tyrosine phosphorylation without affecting the p34cdc2 concentration. These results show that, as it is synthesized, cyclin B binds and recruits p34cdc2 for tyrosine phosphorylation; this inactive complex then requires the completion of DNA replication before it can be turned into fully active MPF. These results fully confirm recent data obtained in vitro with exogenous cyclin added to cycloheximide‐treated Xenopus egg extracts.