Nuclear translocation of Cyclin B1 marks the restriction point for terminal cell cycle exit in G2 phase.
Nuclear translocation of Cyclin B1 marks the restriction point for terminal cell cycle exit in G2 phase.
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DOI：
10.4161/15384101.2015.945831
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
Lindqvist A
中科院分区：
文献类型：
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作者：
Müllers E;Silva Cascales H;Jaiswal H;Saurin AT;Lindqvist A
DNA 损伤后，细胞周期进程会暂时受阻，以避免突变的传播。虽然转化细胞在很大程度上保持了从细胞周期停滞中恢复的能力，但经过 G1/S 转变的未转化细胞失去了有丝分裂诱导剂，从而失去了恢复细胞分裂的能力。这种永久的细胞周期退出取决于 p21、p53 和 APC/CCdh1。然而，永久细胞周期退出何时以及如何发生仍不清楚。在这里，我们研究了在内源基因座表达与 eYFP 融合的 Cyclin B1 的单细胞中对 DNA 损伤的细胞周期反应。我们发现 DNA 损伤后，Cyclin B1-eYFP 继续积累至阈值水平，仅在 G2 期达到阈值水平。高于此阈值，APC/CCdh1 介导的细胞周期蛋白 B1-eYFP 降解所需的 p21 和 p53 依赖性核转位就会启动。因此，细胞周期退出与 DNA 损伤反应的激活以与 Cyclin B1 水平相关的方式脱钩，表明 G2 活性直接影响细胞周期退出的决定。一旦发生Cyclin B1-eYFP核转位，检查点抑制就不能再促进有丝分裂进入或有丝分裂诱导物的重新表达，这表明Cyclin B1核转位标志着G2期永久细胞周期退出的限制点。
Upon DNA damage, cell cycle progression is temporally blocked to avoid propagation of mutations. While transformed cells largely maintain the competence to recover from a cell cycle arrest, untransformed cells past the G1/S transition lose mitotic inducers, and thus the ability to resume cell division. This permanent cell cycle exit depends on p21, p53, and APC/CCdh1. However, when and how permanent cell cycle exit occurs remains unclear. Here, we have investigated the cell cycle response to DNA damage in single cells that express Cyclin B1 fused to eYFP at the endogenous locus. We find that upon DNA damage Cyclin B1-eYFP continues to accumulate up to a threshold level, which is reached only in G2 phase. Above this threshold, a p21 and p53-dependent nuclear translocation required for APC/CCdh1-mediated Cyclin B1-eYFP degradation is initiated. Thus, cell cycle exit is decoupled from activation of the DNA damage response in a manner that correlates to Cyclin B1 levels, suggesting that G2 activities directly feed into the decision for cell cycle exit. Once Cyclin B1-eYFP nuclear translocation occurs, checkpoint inhibition can no longer promote mitotic entry or re-expression of mitotic inducers, suggesting that nuclear translocation of Cyclin B1 marks the restriction point for permanent cell cycle exit in G2 phase.