α-粒子诱发BEP2D细胞恶性转化中DNA修复基因DNA-PK的表达和突变分析

MUTATIONS AND EXPRESSION CHANGES OF DNA-PK GENES DETECTED IN THE MALIGNANT TRANSFORMED BEP2D CELLS INDUCED BY α-PARTICLES EXPOSURE

目的 :研究α 粒子诱发人支气管上皮细胞 (BEP2D)恶性转化中DNA修复基因DNA PK的结构和表达变化。方法 :用Northernblot杂交检测基因转录水平 ,聚合酶链式反应 单链构象多态性 (PCR SSCP)分析基因编码序列结构变化。结果 :癌变细胞中DNA修复基因Ku70 (XRCC 6 )的编码碱基发生突变 ,第 114 8～ 115 3位点由AGGATC突变为GAGTAC ,致使编码的氨基酸由RI变为EY ;细胞恶性转化过程中 ,DNA修复基因DNA PKcs(XRCC 7)的表达发生改变 ,在恶性转化早期即α 粒子照射后第 2 1代就已被抑制 ,但发生癌变 (第 35代 )后 ,部分细胞克隆的该基因表达又重新上调。结论 :DNA修复基因DNA PK的结构和表达的变化 ,导致细胞DNA修复能力缺陷 ,基因组不稳定性增加 ,是α 粒子癌变的分子机制之一。

Purpose: To detect the mutations and expression changes of DNA PK genes in the transformed human bronchial epithelial cells (BEP2D) induced by α particles. Methods: Mutations were detected with PCR SSCP; gene expression was analyzed using Northern blot hybridization. Results: Mutations in the encoding sequence of Ku70(XRCC 6) gene were discovered in the malignant transformed cells. In the process of α particle induced BEP2D transformation, the expression of DNA PKcs gene was depressed at the early stage of transformation, and was up regulated again in some of the malignant transformants. Conclusion: The mutations and depressed expression of DNA repair genes lead to the deficiency of DNA DSBs repair capacity, which in turn might result in genomic instability. These events could play an important role in the malignant transformation of BEP2D cells induced by α particles exposure.