Growth of persistent foci of DNA damage checkpoint factors is essential for amplification of G1 checkpoint signaling
Growth of persistent foci of DNA damage checkpoint factors is essential for amplification of G1 checkpoint signaling
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DOI：
10.1016/j.dnarep.2007.11.011
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发表时间：
2008-03-01
期刊：
影响因子：
3.8
通讯作者：
Suzuki, Keiji
中科院分区：
文献类型：
--
作者：
Yamauchi, Motohiro;Oka, Yasuyoshi;Suzuki, Keiji
几种DNA损伤检查点因子响应于电离辐射（IR）形成核灶。虽然初始病灶的数量随着DNA双链断裂修复而减少，但仍有部分病灶持续存在。到目前为止，生理作用的持久性病灶一直知之甚少。在这里，我们研究了在正常人二倍体细胞暴露于1戈伊的X射线的Ser 1981磷酸化ATM的病灶。当初始病灶大小约为0.6 μ m时，一个或两个持续病灶（病灶）生长，其直径在IR后24小时达到1.6 μ m或更大的直径。所有生长的磷酸化ATM的持续病灶与Ser 139-磷酸化组蛋白H2 AX、MDC 1、53 BP 1和NBS 1的持续病灶共定位，其也类似地生长。当GO同步化的正常人细胞在1戈伊X射线照射后立即释放并孵育24小时时，生长的大的磷酸化ATM灶（>= 1.6 μ m）很少（平均值为1.5 μ m）。0.9%），而较小的病灶（< 1.6 μ m）经常（av.我们观察到在具有单个生长的磷酸化ATM病灶的细胞中p53在Ser 15处显著磷酸化。此外，ATM抑制剂KU 55933持续抑制磷酸化ATM的病灶生长，完全消除了p53磷酸化。共济失调-毛细血管扩张症（AT）和奈梅亨断裂综合征（NBS）患者的原代成纤维细胞在IR诱导的G1期检查点异常时，其DNA损伤检查点因子的持续灶的生长缺陷，提示DNA损伤检查点因子的持续灶的生长在G1期阻滞中起关键作用，其充分放大G1检查点信号以磷酸化具有有限数目剩余病灶的细胞中的p53。(c)2007 Elsevier B.V保留所有权利。
Several DNA damage checkpoint factors form nuclear foci in response to ionizing radiation (IR). Although the number of the initial foci decreases concomitantly with DNA double-strand break repair, some fraction of foci persists. To date, the physiological role of the persistent foci has been poorly understood. Here we examined foci of Ser1981-phosphorylated ATM in normal human diploid cells exposed to 1 Gy of X-rays. While the initial foci size was approximately 0.6 mu m, the one or two of persistent focus (foci) grew, whose diameter reached 1.6 mu m or more in diameter at 24 h after IR. All of the grown persistent foci of phosphorylated ATM colocalized with the persistent foci of Ser139-phosphorylated histone H2AX, MDC1, 53BP1, and NBS1, which also grew similarly. When GO-synchronized normal human cells were released immediately after 1 Gy of X-rays and incubated for 24h, the grown large phosphorylated ATM foci (>= 1.6 mu m) were rarely (av. 0.9%) observed in S phase cells, while smaller foci (< 1.6 mu m) were frequently (av. 45.9%) found. We observed significant phosphorylation of p53 at Ser15 in cells with a single grown phosphorylated ATM focus. Furthermore, persistent inhibition of foci growth of phosphorylated ATM by an ATM inhibitor, KU55933, completely abrogated p53 phosphorylation. Defective growth of the persistent IR-induced foci was observed in primary fibroblasts derived from ataxia-telangiectasia (AT) and Nijmegen breakage syndrome (NBS) patients, which were abnormal in IR-induced G1 checkpoint.These results indicate that the growth of the persistent foci of the DNA damage checkpoint factors plays a pivotal role in G1 arrest, which amplifies G1 checkpoint signals sufficiently for phosphorylating p53 in cells with a limited number of remaining foci. (c) 2007 Elsevier B.V All rights reserved.