ATM and DNA-PK function redundantly to phosphorylate H2AX after exposure to ionizing radiation
ATM and DNA-PK function redundantly to phosphorylate H2AX after exposure to ionizing radiation
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DOI：
10.1158/0008-5472.can-03-3207
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发表时间：
2004-04-01
期刊：
影响因子：
11.2
通讯作者：
Jeggo, PA
中科院分区：
文献类型：
--
作者：
Stiff, T;O'Driscoll, M;Jeggo, PA
H2AX 磷酸化是响应 DNA 损伤的早期步骤。人们普遍认为，ATM（共济失调毛细血管扩张突变蛋白）会磷酸化 H2AX 以响应 DNA 双链断裂 (DSB)。 DNA 依赖性蛋白激酶 (DNA-PK) 是否在这种反应中发挥作用尚不清楚。在这里，我们发现，在人类成纤维细胞和缺乏 DNA-PK 或 ATM 的小鼠胚胎成纤维细胞中，暴露于电离辐射 (IR) 后，H2AX 磷酸化发生的程度相似，但在经 LY294002（一种特异性抑制 DNA-PK 的药物）处理的 ATM 缺陷细胞中，H2AX 磷酸化被消除。此外，我们发现 DNA-PK 和 ATM 失活是消除鸡细胞中 IR 诱导的 H2AX 磷酸化所必需的。我们证实，非复制细胞中 DSB 诱导的 H2AX 磷酸化与 ATR（共济失调毛细血管扩张和 Rad3 相关蛋白）无关。综上所述，我们得出结论，在大多数正常生长条件下，IR 诱导的 H2AX 磷酸化可以通过 ATM 和 DNA-PK 以冗余、重叠的方式进行。相比之下，DNA-PK 不能磷酸化参与检查点反应的其他蛋白质，包括染色质相关的 Rad17。然而，通过磷酸化 H2AX，DNA-PK 可以促进损伤反应蛋白 MDC1 和 53BP1 在 DSB 位点的存在。
H2AX phosphorylation is an early step in the response to DNA damage. It is widely accepted that ATM (ataxia telangiectasia mutated protein) phosphorylates H2AX in response to DNA double-strand breaks (DSBs). Whether DNA-dependent protein kinase (DNA-PK) plays any role in this response is unclear. Here, we show that H2AX phosphorylation after exposure to ionizing radiation (IR) occurs to similar extents in human fibroblasts and in mouse embryo fibroblasts lacking either DNA-PK or ATM but is ablated in ATM-deficient cells treated with LY294002, a drug that specifically inhibits DNA-PK. Additionally, we show that inactivation of both DNA-PK and ATM is required to ablate IR-induced H2AX phosphorylation in chicken cells. We confirm that H2AX phosphorylation induced by DSBs in nonreplicating cells is ATR (ataxia telangiectasia and Rad3-related protein) independent. Taken together, we conclude that under most normal growth conditions, IR-induced H2AX phosphorylation can be carried out by ATM and DNA-PK in a redundant, overlapping manner. In contrast, DNA-PK cannot phosphorylate other proteins involved in the checkpoint response, including chromatin-associated Rad17. However, by phosphorylating H2AX, DNA-PK can contribute to the presence of the damage response proteins MDC1 and 53BP1 at the site of the DSB.