ATM基因对^(60)Co γ射线照射后AT细胞hTERT表达的影响

Study on effects of ATM gene on expression of hTERT in AT cells exposed to ^(60)Co γ -rays

目的研究外源性ATM基因对电离辐射照射的毛细血管扩张-共济失调症(ataxiatelangiectasia,AT)患者皮肤的成纤维细胞系AT细胞(AT5BIVA)hTERT mRNA和蛋白表达的影响。方法以正常人皮肤的成纤维细胞系GM细胞(GM0639)为对照,应用RT-PCR与Western blot实验方法,观察经0、1、3和5Gy(剂量率1.0Gy/min)60Coγ射线照射后,AT细胞、空载体AT细胞、ATM+-AT细胞和GM细胞的hTERT mRNA和蛋白表达的变化。结果未照射时,除GM细胞外,其余各细胞均有hTERTmRNA和蛋白的表达;ATM+-AT细胞的hTERTmRNA和蛋白表达量较AT细胞明显下降(P<0.05);ATM+-AT细胞的hTERT mRNA和蛋白表达量仍然明显高于GM细胞的hTERT mRNA表达量。在1～5Gy剂量范围内,AT、空载体AT、ATM+-AT和GM细胞的hTERT mRNA和蛋白表达量呈剂量依赖性增加;在相同照射剂量点,ATM+-AT细胞的hTERT mRNA表达量较AT细胞均有明显降低(P<0.05)。结论电离辐射可诱导细胞hTERT mRNA和蛋白的表达;并且细胞hTERT mRNA和蛋白表达量呈剂量依赖性增加;外源性ATM基因可下调AT细胞hTERT mRNA和蛋白的表达。推测端粒酶参与电离辐射诱导DNA损伤的修复。

Objective To study the effects of exogenous ATM gene on mRNA and protein expression of hTERT （human telomerase reverse transcriptase, hTERT） of a fibroblast cell line （AT5BIVA cells,At cells for short） established from skin of the ataxia telangiectasia （AT） patients. Methods After the following cells had been exposed to 0, 1, 3, 5 Gy of ^60Co γ-rays, RT-PCR and Western blotting were used to observe the mRNA and protein expressions of hTERT in AT, PEBST（ blank vector）-AT, ATM^＋ （AT gene mutated）-AT and GM cells, respectively. The GM（GM0639） cells were used as the normal control in this experiment. Results Except for GM ceils, there were mRNA and protein expressions of hTERT in all AT, PEBST-AT and ATM^＋ -AT ceils before exposure to ionizing radiation. However, the mRNA and protein expressions of hTERT in ATM^＋ -AT ceils weve significantly lower than those in AT ceils, but still higher than those in GM ceils （P 〈 0.05）. After exposure, the mRNA and protein expressions of hTERT in AT, PEBST-AT, ATM^＋ -AT and GM ceils were increased dose- dependently from 1Gy to 5Gy. At the same dose point, the mRNA expression of hTERT in ATM^＋ -AT ceils was significantly lower than that of AT ceils. Conclusion Exogenous ATM gene can down-rognlate mRNA and protein expressions of hTERT in AT ceils no matter wheter the latter have been exposed to ionizing radiation or not. The mRNA and protein expressions of hTERT in cells can be induced by ionizing radiation in a dose- dependent manner. Telomerase is speculated on to participate in the repair of DNA damaged induced by ionizing radiation.