DNA-DAMAGE TRIGGERS A PROLONGED P53-DEPENDENT G(1) ARREST AND LONG-TERM INDUCTION OF CIP1 IN NORMAL HUMAN FIBROBLASTS
DNA-DAMAGE TRIGGERS A PROLONGED P53-DEPENDENT G(1) ARREST AND LONG-TERM INDUCTION OF CIP1 IN NORMAL HUMAN FIBROBLASTS
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DOI：
10.1101/gad.8.21.2540
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发表时间：
1994-11-01
影响因子：
10.5
通讯作者：
WAHL, GM
中科院分区：
文献类型：
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作者：
DI LEONARDO, A;LINKE, SP;WAHL, GM
肿瘤抑制因子p53是一种细胞周期检查点蛋白，通过介导G（1）阻滞或细胞凋亡来维持遗传稳定性，以响应DNA损伤。最近的报道表明，p53通过转录激活细胞周期蛋白依赖性激酶（Cdk）抑制剂Cip 1导致生长停滞。在这里，我们描述了几种正常人二倍体成纤维细胞（NDF）株和p53缺陷细胞系经0.1-6戈伊γ射线照射后p53依赖性G（1）阻滞的特征。DNA损伤和细胞周期进程分析表明，NDE进入一个长期的停滞状态类似衰老，即使在低剂量的辐射。这与p53通过诱导短暂停滞以修复DNA损伤来确保遗传稳定性的观点形成对比，如对一些骨髓性白血病系所报道的。在G（1）早期至中期（而非晚期）给予γ辐射诱导了阻滞，表明p53检查点仅在G（1）中活跃，直到细胞在G（1）限制点进入S期。能够进入S期的辐照G（0）细胞分数作为剂量的函数的对数线性图与单次击中动力学一致。细胞遗传学分析结合辐射剂量数据表明，只有一个或少量的未修复的DNA断裂可能足以导致逮捕。这种停滞还与p53蛋白、Cip 1 mRNA和Cip 1蛋白的长期升高相关。我们认为，当限制点前G（1）区存在少量未修复的DNA损伤时，p53通过长期诱导Cip 1介导永久性细胞周期停滞来帮助维持NDE的遗传稳定性。
The tumor suppressor p53 is a cell cycle checkpoint protein that contributes to the preservation of genetic stability by mediating either a G(1) arrest or apoptosis in response to DNA damage. Recent reports suggest that p53 causes growth arrest through transcriptional activation of the cyclin-dependent kinase (Cdk)-inhibitor Cip1. Here, we characterize the p53-dependent G(1) arrest in several normal human diploid fibroblast (NDF) strains and p53 deficient cell lines treated with 0.1-6 Gy gamma radiation. DNA damage and cell cycle progression analyses showed that NDE entered a prolonged arrest state resembling senescence, even at low doses of radiation. This contrasts with the view that p53 ensures genetic stability by inducing a transient arrest to enable repair of DNA damage, as reported for some myeloid leukemia lines. Gamma radiation administered in early to mid-, but not late, G(1) induced the arrest, suggesting that the p53 checkpoint is only active in G(1) until cells commit to enter S phase at the G(1) restriction point. A log-linear plot of the fraction of irradiated G(0) cells able to enter S phase as a function of dose is consistent with single-hit kinetics. Cytogenetic analyses combined with radiation dosage data indicate that only one or a small number of unrepaired DNA breaks may be sufficient to cause arrest. The arrest also correlated with long-term elevations of p53 protein, Cip1 mRNA, and Cip1 protein. We propose that p53 helps maintain genetic stability in NDE by mediating a permanent cell cycle arrest through long-term induction of Cip1 when low amounts of unrepaired DNA damage are present in G(1) before the restriction point.