Nuclear localization of cyclin B1 mediates its biological activity and is regulated by phosphorylation
Nuclear localization of cyclin B1 mediates its biological activity and is regulated by phosphorylation
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DOI：
10.1073/pnas.94.2.502
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发表时间：
1997-01-21
影响因子：
11.1
通讯作者：
Donoghue, DJ
中科院分区：
文献类型：
--
作者：
Li, J;Meyer, AN;Donoghue, DJ
M期促进因子或成熟促进因子是细胞周期G（2）-> M转换的关键调节因子，是cdc 2和B型细胞周期蛋白的复合物。我们以前已经表明，非洲爪蟾细胞周期蛋白BI有5个位点的丝氨酸磷酸化，其中4个映射到最近确定的细胞质滞留信号（CRS），CRS似乎是负责细胞质定位的B型细胞周期蛋白，虽然潜在的机制仍然不清楚。细胞周期蛋白B1的磷酸化不是cdc 2结合或cdc 2激酶活性所必需的。然而，当CRS中的所有Ser磷酸化位点突变为Ala以消除磷酸化时，突变的细胞周期蛋白B1（Ala）失活;活性可以通过将这些残基突变为Glu以模拟磷酸丝氨酸来增强，这表明细胞周期蛋白B1的磷酸化是其生物活性所必需的，在这里，我们表明，生物活性可以恢复到细胞周期蛋白B1（Ala）通过附加一个核定位信号（NLS），或第二个CRS结构域与丝氨酸磷酸化位点突变为Glu，而第二CRS结构域与突变为Ala的Ser磷酸化位点的融合使野生型细胞周期蛋白B1失活。核组蛋白H1激酶活性与野生型NLS靶向细胞核的细胞周期蛋白B1（Ala）相关，而突变型NLS则不相关。这些结果表明，核转位介导细胞周期蛋白B1的生物学活性，并表明细胞周期蛋白B1的CRS结构域内的磷酸化在此过程中起调节作用。此外，鉴于细胞周期蛋白依赖性激酶的体外底物特异性相似，这一研究为细胞周期蛋白亚细胞定位的控制在调节生物学过程中起关键作用的假说提供了直接证据。细胞周期蛋白依赖性激酶-细胞周期蛋白复合物的活性。
M-phase promoting factor or maturation promoting factor, a key regulator of the G(2) --> M transition of the cell cycle, is a complex of cdc2 and a B-type cyclin. We have previously shown that Xenopus cyclin BI has five sites of Ser phosphorylation, four of which map to a recently identified cytoplasmic retention signal (CRS), The CRS appears to be responsible for the cytoplasmic localization of B-type cyclins, although the underlying mechanism is still unclear. Phosphorylation of cyclin B1 is not required for cdc2 binding or cdc2 kinase activity. However, when all of the Ser phosphorylation sites in the CRS are mutated to Ala to abolish phosphorylation, the mutant cyclin B1(Ala) is inactivated; activity can be enhanced by mutation of these residues to Glu to mimic phosphoserine, suggesting that phosphorylation of cyclin B1 is required for its biological activity, Here we show that biological activity can be restored to cyclin B1(Ala) by appending either a nuclear localization signal (NLS), or a second CRS domain with the Ser phosphorylation sites mutated to Glu, while fusion of a second CRS domain with the Ser phosphorylation sites mutated to Ala inactivates wild-type cyclin B1. Nuclear histone H1 kinase activity was detected in association with cyclin B1(Ala) targeted to the nucleus by a wild-type NLS, but not by a mutant NLS. These results demonstrate that nuclear translocation mediates the biological activity of cyclin B1 and suggest that phosphorylation within the CRS domain of cyclin B1 plays a regulatory role in this process, Furthermore, given the similar in vitro substrate specificity of cyclin dependent kinases, this investigation provides direct evidence for the hypothesis that the control of subcellular localization of cyclins plays a key role in regulating the biological activity of cyclin-dependent kinase-cyclin complexes.