SCFβ-TRCP links Chk1 signaling to degradation of the Cdc25A protein phosphatase
SCFβ-TRCP links Chk1 signaling to degradation of the Cdc25A protein phosphatase
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DOI：
10.1101/gad.1157503
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发表时间：
2003-12-15
影响因子：
10.5
通讯作者：
Harper, JW
中科院分区：
文献类型：
--
作者：
Jin, JP;Shirogane, T;Harper, JW
真核细胞通过激活蛋白激酶介导的促进细胞周期停滞和DNA修复的信号通路来响应DNA损伤和停滞的复制叉。细胞周期阻滞程序的中心靶标是Cdc 25 A蛋白磷酸酶。Cdc 25 A是进入S期所必需的，并使酪氨酸-15磷酸化的Cdk 1（Cdc 2）和Cdk 2（细胞分裂的正调节剂）去磷酸化。Cdc 25 A在S期不稳定，通过泛素-蛋白酶体途径降解，但其周转率在DNA损伤时增强。虽然基础和DNA损伤诱导的营业额取决于ATM-Chk 2和ATR-Chk 1途径，这些激酶如何参与泛素连接酶机制是未知的。在这里，我们证明了一个要求SCF β-TRCP在Cdc 25 A营业额在一个未受干扰的细胞周期和DNA损伤的反应。β-TRCP的耗尽使Cdc 25 A稳定，导致Cdk 2活性过度活跃。SCF β-TRCP在体外促进Chk 1依赖的Cdc 25 A泛素化，这涉及丝氨酸76，一个已知的Chk 1磷酸化位点。然而，通过β-TRCP识别Cdc 25 A通过Cdc 25 A中含有磷酸丝氨酸79和磷酸丝氨酸82的非典型磷酸降解决定子发生，这些位点不被Chk 1靶向。这些数据表明，Cdc 25 A营业额比以前认识到的更复杂，并建议在Chk 1依赖Cdc 25 A营业额的额外激酶的作用。
Eukaryotic cells respond to DNA damage and stalled replication forks by activating protein kinase-mediated signaling pathways that promote cell cycle arrest and DNA repair. A central target of the cell cycle arrest program is the Cdc25A protein phosphatase. Cdc25A is required for S-phase entry and dephosphorylates tyrosine-15 phosphorylated Cdk1 (Cdc2) and Cdk2, positive regulators of cell division. Cdc25A is unstable during S-phase and is degraded through the ubiquitin-proteasome pathway, but its turnover is enhanced in response to DNA damage. Although basal and DNA-damage-induced turnover depends on the ATM-Chk2 and ATR-Chk1 pathways, how these kinases engage the ubiquitin ligase machinery is unknown. Here, we demonstrate a requirement for SCFbeta-TRCP in Cdc25A turnover during an unperturbed cell cycle and in response to DNA damage. Depletion of beta-TRCP stabilizes Cdc25A, leading to hyperactive Cdk2 activity. SCFbeta-TRCP promotes Chk1-dependent Cdc25A ubiquitination in vitro, and this involves serine 76, a known Chk1 phosphorylation site. However, recognition of Cdc25A by beta-TRCP occurs via a noncanonical phosphodegron in Cdc25A containing phosphoserine 79 and phosphoserine 82, sites that are not targeted by Chk1. These data indicate that Cdc25A turnover is more complex than previously appreciated and suggest roles for an additional kinase(s) in Chk1-dependent Cdc25A turnover.