中文摘要：

目的 研究RNA干扰p21基因对X射线诱导细胞周期解耦联的影响。方法 构建RNA干扰质粒pSilencer3．1-H1 neo-p21，并采用脂质体转染将质粒转入EL-4细胞。采用单克隆抗体免疫荧光标记及流式细胞术（FCM）检测蛋白表达的变化。采用碘化丙啶（PI）荧光标记及FCM检测多倍体细胞数的变化。结果 量效实验证实，1．0～4．0 Gy X射线照射后24h，EL-4细胞中P21蛋白表达与对照组相比较显著增高。时效实验证实，4．0Gy X射线照射后8～72h，EL-4细胞中P21蛋白表达与对照组相比较显著增高。实验证实，0．5～6．0Gy X射线照射后，EL4细胞的八倍体细胞数未见明显变化，X射线照射不诱导EL4细胞周期解耦联。RNA干扰实验证实，p21基因沉默后，P21蛋白表达于4．0Gy照射后24及48h，干扰质粒组与空质粒对照组相比较显著降低；与此同时，干扰质粒组的八倍体细胞数与空质粒组相比较显著增高。结论 RNA干扰p21基因使P21蛋白表达抑制后，X射线照射可诱导EL4细胞周期解耦联。提示，P21蛋白可能在电离辐射诱导细胞周期解耦联中起重要作用。

英文摘要：

Objective To investigate the effect of RNAi p21 gene on uncoupling of EL-4 cells induced by X-irradiation. Methods Construction of RNAi p21 plasmid of pSilencer3.1-H1 neo-p21 was performed. Lipofectamine transfection assay was used to transfer the p21siRNA into EL-4 cells. Fluorescent staining and flow cytometry （FCM） analysis were employed for measurement of protein expression. Fluorescent staining of propidium iodide （PI） and FCM were used for measurement of polyploid cells. Results In dose-effect experiment it was found that the expression of P21 protein of EL-4 cells increased significantly 24 h after Xirradiation with different doses compared with sham-irradiated control. In time course experiment it was found that the expression of P21 protein of EL-4 cells increased significantly at 8 h to 72 h after 4.0 Gy X-irradiation compared with sham-irradiated control. The results showed that the number of polyploid cells in EL-4 cells was not changed markedly after X-irradiation with doses of 0.5-6.0 Gy. After RNA interference with p21 gene, the expression of P21 protein of EL-4 cells decreased significantly 24 h and 48 h after 4.0 Gy X-irradiation in transfection of plasmid of pSilencer3.1-H1 neo-p21 compared with transfection of plasmid of pSilencer3.1-H1 neo control. And at the same time, the number of polyploid cells in EL-4 cells was increased significantly in transfection of plasmid of pSilencer3.1-H1 neo-p21 compared with transfection of plasmid of pSilencer3.1-H1 neo control. Conclusions Uncoupling could be induced by X-irradiation in EL-4 cells following RNAi p21 gene, suggesting that P21 protein may play an important role in uncoupling induced by X-rays.