DNA damage-induced cell-cycle phase regulation of p53 and p21waf1 in normal and ATM-defective cells
DNA damage-induced cell-cycle phase regulation of p53 and p21waf1 in normal and ATM-defective cells
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DOI：
10.1038/sj.onc.1207086
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发表时间：
2003-10-30
期刊：
影响因子：
8
通讯作者：
Mizutani, S
中科院分区：
文献类型：
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作者：
Delia, D;Fontanella, E;Mizutani, S
atm依赖性的p53积累和p21（waf1）的诱导是DNA损伤后G1细胞周期检查点阻滞的关键事件。在无atm的AT细胞中，尽管p53和p21（waf1）反应在动力学上延迟和数量上减少，但G1检查点实际上被破坏了，这表明这些蛋白质在G1中到达得太晚，无法执行阻滞。由于确切的机制尚不清楚，我们研究了对伽马辐射（IR）产生的DNA双链断裂的反应，以确定ATM缺乏是否影响这些分子的细胞周期阶段调节。我们发现，在照射后，正常LCL-N细胞在细胞周期的所有阶段都显著增加p53的水平，而AT细胞在G1期没有显示任何p53的增加。此外，在LCL-N中，p21（waf1）在G1和G2-M中被诱导，而在AT细胞中，这种诱导部分出现在G2-M中，但在G1中没有，这表明由于ATM缺乏，p53和p21（waf1）的细胞周期阶段调节不同。LCL-N和AT细胞中p53靶向激酶ATR和DNA-PK的水平和催化活性在整个细胞周期中非常相似，无论是在IR之前还是之后，因此排除了这些激酶的阶段特异性活性。总的来说，我们的研究结果表明，在atm缺陷细胞中，p53依赖性p21（waf1）对DNA损伤的反应不仅在数量上降低，而且在G1期被特异性抑制，从而为AT细胞中G1检查点的严重破坏提供了机制解释。
The ATM-dependent accumulation of p53 and induction of p21(waf1) are key events for G1 cell-cycle checkpoint arrest following DNA damage. In ATM-null AT cells, even though the p53 and p21(waf1) responses are kinetically delayed and quantitatively reduced, the G1 checkpoint is virtually disrupted, suggesting that these proteins arrive too late in G1 to enforce the arrest. As the precise mechanism remains unclear, we examined the response to DNA double-strand breaks generated by gamma-radiation (IR), to determine if ATM deficiency affects the cell-cycle phase regulation of these molecules. We find that, after irradiation, whereas normal LCL-N cells markedly increase their levels of p53 in all phases of the cell cycle, AT cells fail to show any p53 increase in the G1 phase. In addition, whereas in LCL-N p21(waf1) is induced in G1 and G2-M, in AT cells this induction is partly seen in G2-M, but not in G1, indicating a different cell-cycle phase regulation of p53 and p21(waf1) as a result of ATM deficiency. The levels and catalytic activity of the p53-targeting kinases ATR and DNA-PK in LCL-N and AT cells are very similar throughout the cell cycle, both before and after IR, thus excluding a phase-specific activity for these kinases. Collectively, our findings demonstrate that, in ATM-deficient cells, the p53-dependent p21(waf1) response to DNA damage is not only quantitatively reduced, but also specifically suppressed in the G1 phase, thus providing a mechanistic explanation for the severe disruption of the G1 checkpoint in AT cells.