60Coγ射线对盐诱导激酶2的诱导表达作用

60Coγ-ray irradiation induced expression of salt-inducible kinase 2

目的探讨电离辐射对盐诱导激酶2（SIK2）蛋白和mRNA的诱导表达作用及细胞周期相关性。方法HepG2细胞用60Coγ射线照射，蛋白质印迹法和实时定量PCR法分别检测细胞的SIK2蛋白和mRNA的表达，胸腺嘧啶双阻滞法同步化细胞，流式细胞术测定细胞周期的变化。结果HepG2细胞2Gy照射后4、6、10h，SIK2蛋白表达显著增加（t=3．00、3．98、4．17，P〈0．05）；10Gy大剂量照射后，SIK2蛋白表达增加的趋势与2Gy一致，但增加的幅度较前者低。2和10Gy照射后SIK2基因mRNA均在10h出现了增加（t=4．54、2．74，P〈0．05）。照后10h出现了细胞G：／M阻滞高峰。利用同步化细胞分析表明，细胞周期不同时相中SIK2mRNA的表达无明显差别。结论2和10Gy照射均能诱导SIK2蛋白表达增加，2Gy的作用更加明显。细胞照射后10h，SIK2mRNA的表达水平增加，但与辐射诱发细胞G2／M期阻滞引起不同时相细胞的分布变化无关。

Objective To explore the expression changes of SIK2 in both protein and mRNA levels in response to ionizing radiation and its potential relationship with the cell cycle distribution alteration. Methods HepG2 cells were irradiated with 6~Co ~/-rays. Western blot and Real-time PCR were used to detect the level of the protein and mRNA, respectively. TdR double-blocking method was used to synchronize cell and the cell cycle distribution was analyzed by flow cytometry. Results The protein level of SIK2 was significantly increased at 4, 6, and 10 h （t = 3.00, 3.98, 4.17, P 〈 O. 05） after 2 Gy irradiation. The same increasing tendency of SIK2 protein level was observed in the cells irradiated by 10 Gy of ^-rays, hut the increased extent was less than that induced by 2 Gy. A significantly increased mRNA expression of SIK2 was detected at about 10 h after 2 or 10 Gy irradiation （t = 4.54, 2. 74, P 〈 0. 05 ）. The G2/M arrest approached to a peak value at 10 h after 2 and 10 Gy irradiation. The result of mRNA level analysis indicated that there was no obvious change among different cell cycle phases of the synchronized cells. Conclusions The level of SIK2 protein can he significantly induced by both 2 Gy and l0 Gy irradiation, and a part of the increased protein level is attributed to the induction of mRNA transcription 10 h post-irradiation. The increased SIK2 mRNA expression is not the consequence of the cell cycle alteration caused by irradiation-induced G2/M arrest.