Majone Franca, Luisetto Roberto, Zamboni Daniela, Iwanaga Yoichi, Jeang Kuan-Teh
Department of Biology, University of Padua, Padua, Italy.
Retrovirology. 2005 Jul 13;2:45. doi: 10.1186/1742-4690-2-45.
The HTLV-1 Tax oncoprotein rapidly induces cytogenetic damage which can be measured by a significant increase in the number of micronuclei (MN) in cells. Tax is thought to have both aneuploidogenic and clastogenic effects. To examine the cellular target for Tax which might mechanistically explain the clastogenic phenomenon, we tested the ability of Tax to induce MN in rodents cells genetically defective for either the Ku80 protein or the catalytic subunit of DNA protein kinase (DNAPKcs). We found that cells genetically mutated in Ku80 were refractory to Tax's induction of MN while cells knocked-out for DNAPKcs showed increased number of Tax-induced MN. Using a cytogenetic method termed FISHI (Fluorescent In Situ Hybridization and Incorporation) which measures the number of DNA-breaks in cells that contained unprotected 3'-OH ends, we observed that Tax increased the prevalence of unprotected DNA breaks in Ku80-intact cells, but not in Ku80-mutated cells. Taken together, our findings suggest Ku80 as a cellular factor targeted by Tax in engendering clastogenic DNA damage.
人嗜T淋巴细胞病毒1型（HTLV-1）的Tax癌蛋白能迅速诱导细胞遗传损伤，这可通过细胞中微核（MN）数量的显著增加来衡量。Tax被认为具有非整倍体生成和致断裂作用。为了研究Tax的细胞靶点，从机制上解释致断裂现象，我们测试了Tax在Ku80蛋白或DNA蛋白激酶催化亚基（DNAPKcs）基因缺陷的啮齿动物细胞中诱导MN的能力。我们发现，Ku80基因发生突变的细胞对Tax诱导MN具有抗性，而DNAPKcs基因敲除的细胞中Tax诱导的MN数量增加。使用一种称为FISHI（荧光原位杂交与掺入）的细胞遗传学方法，该方法可测量含有未受保护3'-OH末端的细胞中的DNA断裂数量，我们观察到Tax增加了Ku80完整细胞中未受保护DNA断裂的发生率，但在Ku80突变细胞中未增加。综上所述，我们的研究结果表明，Ku80是Tax在导致致断裂性DNA损伤过程中的细胞靶点。
