Unité Mixte de Recherche 5239, Centre National de la Recherche Scientifique, Ecole Normale Supérieure de Lyon, Lyon, France.
Cancer Res. 2012 Apr 15;72(8):2006-16. doi: 10.1158/0008-5472.CAN-11-2562.
Altered expression of the INT6 gene, encoding the e subunit of the translational initiation factor eIF3, occurs in human breast cancers, but how INT6 relates to carcinogenesis remains unestablished. Here, we show that INT6 is involved in the DNA damage response. INT6 was required for cell survival following γ-irradiation and G(2)-M checkpoint control. RNA interference-mediated silencing of INT6 reduced phosphorylation of the checkpoint kinases CHK1 and CHK2 after DNA damage. In addition, INT6 silencing prevented sustained accumulation of ataxia telangiectasia mutated (ATM) at DNA damage sites in cells treated with γ-radiation or the radiomimetic drug neocarzinostatin. Mechanistically, this result could be explained by interaction of INT6 with ATM, which together with INT6 was recruited to the sites of DNA damage. Finally, INT6 silencing also reduced ubiquitylation events that promote retention of repair proteins at DNA lesions. Accordingly, accumulation of the repair factor BRCA1 was defective in the absence of INT6. Our findings reveal unexpected and striking connections of INT6 with ATM and BRCA1 and suggest that the protective action of INT6 in the onset of breast cancers relies on its involvement in the DNA damage response.
INT6 基因（编码翻译起始因子 eIF3 的 e 亚基）的表达改变发生在人类乳腺癌中，但 INT6 与致癌作用的关系尚不清楚。在这里，我们表明 INT6 参与 DNA 损伤反应。INT6 在 γ 辐射和 G2-M 检查点控制后细胞存活中是必需的。RNA 干扰介导的 INT6 沉默减少了 DNA 损伤后检查点激酶 CHK1 和 CHK2 的磷酸化。此外，INT6 沉默可防止在用 γ 辐射或放射模拟药物 neocarzinostatin 处理的细胞中，ATM（共济失调毛细血管扩张突变）在 DNA 损伤部位的持续积累。从机制上讲，这一结果可以通过 INT6 与 ATM 的相互作用来解释，INT6 与 ATM 一起被募集到 DNA 损伤部位。最后，INT6 沉默也减少了促进修复蛋白在 DNA 损伤处保留的泛素化事件。因此，在缺乏 INT6 的情况下，修复因子 BRCA1 的积累是有缺陷的。我们的发现揭示了 INT6 与 ATM 和 BRCA1 的出人意料的惊人联系，并表明 INT6 在乳腺癌发生中的保护作用依赖于其参与 DNA 损伤反应。
