Spy1 enhances phosphorylation and degradation of the cell cycle inhibitor p27
Spy1 enhances phosphorylation and degradation of the cell cycle inhibitor p27
复制标题
DOI：
10.4161/cc.6.15.4520
复制
发表时间：
2007-08-01
期刊：
影响因子：
4.3
通讯作者：
Donoghue, Daniel J.
中科院分区：
文献类型：
--
作者：
McAndrew, Christopher W.;Gastwirt, Randy F.;Donoghue, Daniel J.
细胞周期蛋白依赖性激酶抑制剂 (CKI) p27(Kip1) 与细胞周期蛋白 E/CDK2 复合物结合，防止过早进入 S 期。在 G(1) 晚期和整个 S 期，T187 处的 p27 磷酸化导致其随后降解，从而减轻 CDK2 抑制，促进细胞周期进展。然而，触发 CDK2 复合物磷酸化 p27 的关键事件仍不清楚。利用重组蛋白，我们证明人 Speedy (Spy1) 在体外激活 CDK2 在 T187 处磷酸化 p27。将 Spy1 或 Spy1/CDK2 添加到预先形成的受抑制的细胞周期蛋白 E/CDK2/p27 复合物中也促进了这种磷酸化。此外，在体外，Spy1 保护细胞周期蛋白 E/CDK2 免受 p27 对组蛋白 H1 的抑制。 U2OS 细胞中诱导型 Spy1 表达降低了内源性 p27 和外源性 p27(WT) 的水平，但不降低 p27(T187A) 突变体的水平。此外，同步 HeLa 细胞中的 Spy1 表达增强了 G(1) 晚期和整个 S 期的 T187 磷酸化和内源性 p27 的降解。我们的研究提供的证据表明，Spy1 表达可增强 G(1) 晚期和整个 S 期期间 CDK2 依赖性 p27 的降解。
The cyclin dependent kinase inhibitor (CKI) p27(Kip1) binds to cyclin E/CDK2 complexes and prevents premature S-phase entry. During late G(1) and throughout S-phase, p27 phosphorylation at T187 leads to its subsequent degradation, which relieves CDK2 inhibition to promote cell cycle progression. However, critical events that trigger CDK2 complexes to phosphorylate p27 remain unclear. Utilizing recombinant proteins, we demonstrate that human Speedy ( Spy1) activates CDK2 to phosphorylate p27 at T187 in vitro. Addition of Spy1 or Spy1/CDK2 to a preformed, inhibited cyclin E/CDK2/p27 complex also promoted this phosphorylation. Furthermore, Spy1 protected cyclin E/CDK2 from p27 inhibition toward histone H1, in vitro. Inducible Spy1 expression in U2OS cells reduced levels of endogenous p27 and exogenous p27(WT), but not a p27(T187A) mutant. Additionally, Spy1 expression in synchronized HeLa cells enhanced T187 phosphorylation and degradation of endogenous p27 in late G(1) and throughout S-phase. Our studies provide evidence that Spy1 expression enhances CDK2-dependent p27 degradation during late G(1) and throughout S-phase.