DNA polymerase η, the product of the xeroderma pigmentosum variant gene and a target of p53, modulates the DNA damage checkpoint and p53 activation
DNA polymerase η, the product of the xeroderma pigmentosum variant gene and a target of p53, modulates the DNA damage checkpoint and p53 activation
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DOI：
10.1128/mcb.26.4.1398-1413.2006
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发表时间：
2006-02-01
影响因子：
5.3
通讯作者：
Chen, XB
中科院分区：
文献类型：
--
作者：
Liu, G;Chen, XB
DNA 聚合酶 eta (PolH) 是色素性干皮病变体 (XPV) 基因的产物，也是一种用于跨损伤合成的已充分表征的 Y 家族 DNA 聚合酶。来自 XPV 患者的细胞无法准确地绕过紫外线光产物和 DNA 加合物，从而获得基因突变。在这里，我们发现电离辐射或化疗剂诱导的DNA断裂可以上调PolH，并且PolH的敲除使细胞以p53依赖性方式抵抗多种细胞系和细胞类型中DNA断裂诱导的细胞凋亡。为了探索潜在的机制，我们检查了 DNA 断裂时 p53 的激活，发现 p53 激活在 PolH 敲低细胞和 PolH 无效的原代成纤维细胞中受损。重要的是，将 PolH 重建到 PolH 敲低细胞中可以恢复 p53 的激活。此外，我们提供的证据表明，在 DNA 断裂时，PolH 与磷酸化的 ATM 部分共定位于 gamma-H2AX 焦点，并且 PolH 的敲低会损害 ATM 磷酸化 Chk2 和 p53。然而，当 DNA 受到紫外线损伤时，PolH 敲低细胞表现出两种相反的时间反应：在早期，PolH 敲低会抑制 p53 活化，并以 p53 依赖性方式使细胞抵抗紫外线诱导的细胞凋亡；在后期，PolH 的敲低会抑制 DNA 修复，导致 p53 持续激活，并以 p53 依赖性和非 p53 依赖性方式增加细胞凋亡的易感性。综上所述，我们发现 PolH 在 DNA 损伤检查点中具有新的作用，并且 p53 靶标可以调节 DNA 损伤反应并随后调节 p53 激活。
DNA polymerase eta (PolH) is the product of the xeroderma pigmentosum variant (XPV) gene and a well-characterized Y-family DNA polymerase for translesion synthesis. Cells derived from XPV patients are unable to faithfully bypass UV photoproducts and DNA adducts and thus acquire genetic mutations. Here, we found that PolH can be up-regulated by DNA breaks induced by ionizing radiation or chemotherapeutic agents, and knockdown of PolH gives cells resistance to apoptosis induced by DNA breaks in multiple cell lines and cell types in a p53-dependent manner. To explore the underlying mechanism, we examined p53 activation upon DNA breaks and found that p53 activation is impaired in PolH knockdown cells and PolH-null primary fibroblasts. Importantly, reconstitution of PolH into PolH knockdown cells restores p53 activation. Moreover, we provide evidence that, upon DNA breaks, PolH is partially colocalized with phosphorylated ATM at gamma-H2AX foci and knockdown of PolH impairs ATM to phosphor-ylate Chk2 and p53. However, upon DNA damage by UV, PolH knockdown cells exhibit two opposing temporal responses: at the early stage, knockdown of PolH suppresses p53 activation and gives cells resistance to UV-induced apoptosis in a p53-dependent manner; at the late stage, knockdown of PolH suppresses DNA repair, leading to sustained activation of p53 and increased susceptibility to apoptosis in both a p53-dependent and a p53-independent manner. Taken together, we found that PolH has a novel role in the DNA damage checkpoint and that a p53 target can modulate the DNA damage response and subsequently regulate p53 activation.