Department of Bio-materials, DNA Repair Research Center, Chosun University, Gwangju, Chonnam 501-759, Republic of Korea.
Oncogene. 2010 Mar 11;29(10):1431-50. doi: 10.1038/onc.2009.438. Epub 2009 Dec 21.
The p53-inducible gene 3 (PIG3) is originally isolated as a p53 downstream target gene, but its function remains unknown. Here, we report a role of PIG3 in the activation of DNA damage checkpoints, after UV irradiation or radiomimetic drug neocarzinostatin (NCS). We show that depletion of endogenous PIG3 sensitizes cells to DNA damage agents, and impaired DNA repair. PIG3 depletion also allows for UV- and NCS-resistant DNA synthesis and permits cells to progress into mitosis, indicating that PIG3 knockdown can suppress intra-S phase and G2/M checkpoints. PIG3-depleted cells show reduced Chk1 and Chk2 phosphorylation after DNA damage, which may directly contribute to checkpoint bypass. PIG3 exhibited diffuse nuclear staining in the majority of untreated cells and forms discrete nuclear foci in response to DNA damage. PIG3 colocalizes with gamma-H2AX and 53BP1 to sites of DNA damage after DNA damage, and binds to a gamma-H2AX. Notably, PIG3 depletion decreases the efficient induction and maintenance of H2AX phosphorylation after DNA damage. Moreover, PIG3 contributes to the recruitment of 53BP1, Mre11, Rad50 and Nbs1 to the sites of DNA break lesions in response to DNA damage. Our combined results suggest that PIG3 is a critical component of the DNA damage response pathway and has a direct role in the transmission of the DNA damage signal from damaged DNA to the intra-S and G2/M checkpoint machinery in human cells.
p53 诱导基因 3（PIG3）最初作为 p53 的下游靶基因被分离出来，但它的功能仍不清楚。在这里，我们报告了 PIG3 在 DNA 损伤检查点激活中的作用，包括紫外线照射或放射模拟药物新制癌菌素（NCS）。我们发现，内源性 PIG3 的耗竭使细胞对 DNA 损伤剂敏感，并损害 DNA 修复。PIG3 耗竭还允许 UV 和 NCS 抵抗的 DNA 合成，并使细胞进入有丝分裂，表明 PIG3 敲低可以抑制细胞内 S 期和 G2/M 检查点。PIG3 耗竭的细胞在 DNA 损伤后显示 Chk1 和 Chk2 磷酸化减少，这可能直接导致检查点旁路。PIG3 在未经处理的大多数细胞中表现出弥漫性核染色，并且在响应 DNA 损伤时形成离散的核焦点。PIG3 在 DNA 损伤后与 γ-H2AX 和 53BP1 共定位到 DNA 损伤部位，并与 γ-H2AX 结合。值得注意的是，PIG3 耗竭减少了 DNA 损伤后 H2AX 磷酸化的有效诱导和维持。此外，PIG3 有助于在 DNA 损伤后将 53BP1、Mre11、Rad50 和 Nbs1 募集到 DNA 断裂损伤部位。我们的综合结果表明，PIG3 是 DNA 损伤反应途径的关键组成部分，并且在人类细胞中从受损 DNA 到细胞内 S 期和 G2/M 检查点机制的 DNA 损伤信号传递中具有直接作用。
