p53 regulates Cdc2 independently of inhibitory phosphorylation to reinforce radiation-induced G2 arrest in human cells
p53 regulates Cdc2 independently of inhibitory phosphorylation to reinforce radiation-induced G2 arrest in human cells
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p53 独立于抑制性磷酸化调节 Cdc2，以加强辐射诱导的人类细胞 G2 停滞
DOI：
10.1038/sj.onc.1201991
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发表时间：
1998
期刊：
影响因子：
8
通讯作者：
C. Norbury
中科院分区：
文献类型：
--
作者：
Zoe Winters;W. Ongkeko;A. Harris;C. Norbury
我们利用表达温度敏感型p53的人H1299细胞，研究了p53对辐射诱导的G2细胞周期阻滞的影响。γ辐照缺乏p53的细胞在G2期短暂阻滞，Cdc2在Thr14和Tyr15抑制位点广泛磷酸化，Cdc2和细胞周期蛋白B1限制在细胞质中。温度变化对p53的激活导致更持久的G2停搏，这不能被取消检查点的药物所覆盖。令人惊讶的是，这种G2阻滞的增强与Cdc2的抑制性磷酸化的明显缺乏以及Cdc2和细胞周期蛋白B1的核定位有关。虽然在缺乏p53的细胞中，不受抑制性磷酸化影响的A14F15 Cdc2突变体的短暂表达会诱导有丝分裂突变，但p53表达的细胞相对不易受到这种影响。在p53缺失的细胞中，p21WAF1/CIP1的强制表达足以赋予Cdc2的核定位，尽管免疫消耗实验表明，在p53表达的细胞中，只有一小部分Cdc2与p21WAF1/CIP1稳定相关。我们得出的结论是，人类细胞暴露于电离辐射后，p53依赖途径可以促进G2阻滞并伴有核易位，而不是抑制Cdc2的磷酸化。
We have investigated the influence of p53 on radiation-induced G2 cell cycle arrest using human H1299 cells expressing temperature-sensitive p53. Gamma-irradiated cells lacking p53 arrested transiently in G2 with Cdc2 extensively phosphorylated at the inhibitory sites Thr14 and Tyr15, and with both Cdc2 and cyclin B1 restricted to the cytoplasm. Activation of p53 by temperature shift resulted in a more protracted G2 arrest that could not be overridden by checkpoint-abrogating drugs. Surprisingly, this enhancement of G2 arrest was associated with a marked lack of inhibitory phosphorylation of Cdc2 and with the nuclear localization of both Cdc2 and cyclin B1. While transient expression of an A14F15 mutant form of Cdc2 that is not subject to inhibitory phosphorylation induced mitotic catastrophe in cells lacking p53, the p53-expressing cells were relatively refractory to this effect. Enforced expression of p21WAF1/CIP1 was sufficient to confer nuclear localization on Cdc2 in the p53 null cells, though immunodepletion experiments demonstrated that only a small proportion of Cdc2 was stably associated with p21WAF1/CIP1 in the p53-expressing cells. We conclude that a p53-dependent pathway can operate after exposure of human cells to ionising radiation to promote G2 arrest accompanied by nuclear translocation rather than inhibitory phosphorylation of Cdc2.