吉林大学学报(医学版)  2019, Vol. 45 Issue (05): 981-985     DOI: 10.13481/j.1671-587x.20190501

扩展功能

文章信息

唐庚, 史耀庭, 孔维轩, 柯希扬, 李成想, 邱禹淇, 于雷, 杨艳明, 王志成
TANG Geng, SHI Yaoting, KONG Weixuan, KE Xiyang, LI Chengxiang, QIU Yuqi, YU Lei, YANG Yanming, WANG Zhicheng
电离辐射对沉默ATRX的HeLa细胞DNA损伤修复的影响
Effect of ionizing radiation on DNA damage repair in HeLa cells silencing ATRX
吉林大学学报(医学版), 2019, 45(05): 981-985
Journal of Jilin University (Medicine Edition), 2019, 45(05): 981-985
10.13481/j.1671-587x.20190501

文章历史

收稿日期: 2019-01-03
电离辐射对沉默ATRX的HeLa细胞DNA损伤修复的影响
唐庚1 , 史耀庭2 , 孔维轩1 , 柯希扬1 , 李成想1 , 邱禹淇1 , 于雷3 , 杨艳明3 , 王志成1     
1. 吉林大学公共卫生学院国家卫生健康委员会放射生物学重点实验室, 吉林 长春 130021;
2. 黑龙江省农垦总局总医院肿瘤四科, 黑龙江 哈尔滨 150088;
3. 吉林大学第二医院放疗科, 吉林 长春 130041
[摘要]: 目的: 靶向沉默宫颈癌HeLa细胞中α-地中海贫血/精神发育迟滞综合征X染色相关蛋白(ATRX),检测电离辐射对ATRX、γH2AX和Rad51蛋白表达及γH2AX和Rad51焦点数的影响,探讨ATRX参与辐射后HeLa细胞DNA损伤修复的作用。方法: 3条ATRX-shRNA和阴性对照(Control-shRNA)的慢病毒载体转染293T细胞,收集慢病毒并感染HeLa细胞,利用puromycin筛选获得稳定沉默ATRX的细胞系,分别命名为shA1-HeLa、shA2-HeLa、shA3-HeLa和shCon-HeLa,采用Western blotting法检测沉默ATRX效率以及电离辐射后ATRX、γH2AX和Rad51蛋白的表达,采用免疫荧光技术观察shCon-HeLa和shA1-HeLa组中γH2AX和Rad51焦点并计数其数量。结果: shCon-HeLa细胞中可见ATRX蛋白表达,而shA1-HeLa、shA2-HeLa和shA3-HeLa细胞中均无ATRX蛋白表达,表明沉默效率较高。在2和8 Gy剂量照射后1、6和24 h,shCon-HeLa组ATRX蛋白表达量逐渐升高,24 h时表达量最高,且8 Gy照射后1、6和24 h表达量均较高。4 Gy照射后0~6 h,与shCon-HeLa组比较,shA1-HeLa组γH2AX焦点数在1 h明显升高(P < 0.05),而后逐渐降低,但在6 h焦点数仍明显高于shCon-HeLa组(P < 0.01);Rad51焦点数与γH2AX焦点数变化相一致,与shCon-HeLa组比较,shA1-HeLa组Rad51焦点数在1 h明显升高(P < 0.05),在6 h时shA1-HeLa焦点数仍明显高于shCon-HeLa组(P < 0.01)。4 Gy照射后0~16 h,shA1-HeLa组细胞中γH2AX和Rad51蛋白表达量均较shCon-HeLa组增加。结论: 成功获得稳定沉默ATRX的HeLa细胞模型,电离辐射可诱导ATRX蛋白表达量增加,且沉默ATRX的HeLa细胞中γH2AX和Rad51焦点数及蛋白表达量均高于对照组,提示ATRX参与了辐射诱导的DNA损伤修复过程。
关键词: 电离辐射    α-地中海贫血/精神发育迟滞综合征X染色相关蛋白    γH2AX蛋白    Rad51蛋白    DNA损伤    
Effect of ionizing radiation on DNA damage repair in HeLa cells silencing ATRX
TANG Geng1 , SHI Yaoting2 , KONG Weixuan1 , KE Xiyang1 , LI Chengxiang1 , QIU Yuqi1 , YU Lei3 , YANG Yanming3 , WANG Zhicheng1     
1. NHC Key Laboratory of Radiobiology, School of Public Health, Jilin University, Changchun 130021, China;
2. Department of Oneology, General Hospital, Heilongjiang Province Land Reclamation Bureau, Haerbin 150088, China;
3. Department of Radiotherapy, Second Hospital, Jilin University, Changchun 130041, China
[ABSTRACT]: Objective: To silence α-thalassemia/mental retardation syndrome X-linked gene(ATRX) in the cervical cancer HeLa cells, to detect the effect of ionizing radiation on the protein expressions of ATRX, γH2AX, Rad51 and γH2AX, Rad51 foci, and to explore the role of ATRX in DNA damage repair of the HeLa cells after irradiation. Methods: Three ATRX-shRNA and negative Control-shRNA lentiviral vectors were transfected into the 293T cells, and the lentiviruses were collected to infect the HeLa cells; puromycin was used to obtain the HeLa cells stably silencing ATRX named shA1-HeLa, shA2-HeLa, shA3-HeLa, and shCon-HeLa; the silencing efficiency was detected by Western blotting method. After ionizing radiation, the expressions of ATRX, γH2AX, and Rad51 proteins were measured by Western blotting method, and the numbers of γH2AX and Rad51 foci in shCon-HeLa and shA1-HeLa groups were observed and counted by immunofluorescence technique. Results: The ATRX protein expressed in shCon-HeLa cells, but did not express in shA1-HeLa, shA2-HeLa, and shA3-HeLa cells; it indicated that the silencing efficiency was higher. At 1, 6, and 24 h after 2 and 8 Gy irradiation, the ATRX protein expression levels in shCon-HeLa group were increased gradually; it was most at 24 h, and the ATRX was highly expressed at 1, 6, and 24 h after 8 Gy irradiation. Compared with shCon-HeLa group, at 0-6 h after 4 Gy irradiation, the number of γH2AX foci in shA1-HeLa group was significantly increased at 1 h (P < 0.05), then was gradually decreased, but the number of γH2AX foci in shA1-HeLa group was still higher at 6 h (P < 0.01). The number of Rad51 foci was consistent with the changes of γH2AX focus number. Compared with shCon-HeLa group, the number of Rad51 foci was significantly increased at 1 h (P < 0.05), and the number in shA1-HeLa group was still higher at 6 h (P < 0.01). At 0-16 h after 4 Gy irradiation, compared with shCon-HeLa, the expression amounts of γH2AX and Rad51 proteins in shA1-HeLa group were increased. Conclusion: The HeLa cell models silencing ATRX are successfully obtained; ionizing radiation can cause the increase of ATRX expression level; the focus number and the protein expression amounts of γH2AX and Rad51 in HeLa cells silencing ATRX are higher than those in control group, which indicates that ATRX involves in the repair of radiation-induced DNA damage.
KEYWORDS: ionizing radiation     alpha thalassemia/mental retardation syndrome X-linked protein     γH2AX protein     Rad51 protein     DNA damage    

α-地中海贫血/精神发育迟滞综合征X染色体相关蛋白(alpha thalassemia/mental retardation syndrome X-linked protein, ATRX)属于SWI2/SNF2家族成员,具有广泛的生物学功能,参与DNA损伤修复、转录调节和染色质重组等[1-2]ATRX主要定位于细胞富含CCCTAA的端粒末端,且与G-四联体相互作用,是一个重要的DNA二级结构,可能导致DNA复制应激[3-4]。ATRX是一种肿瘤抑制因子,在许多肿瘤细胞中往往也伴随着ATRX的缺失,如U2OS细胞、脑胶质细胞瘤和脂肪肉瘤等[5-6]。肿瘤基因-放射治疗是辐射肿瘤学相关研究的热点,辐射可致DNA损伤,进而引发肿瘤细胞凋亡或坏死,达到治疗肿瘤的目的。DNA损伤方式主要包括单链断裂(single strand breaks,SSB)、双链断裂(double strand break,DSB)、碱基的修饰和丧失碱基位点等,其中DSB最严重[7]。细胞在电离辐射作用后,H2AX在极短时间内迅速磷酸化γH2AX并在DSB位点形成焦点,而后者所形成焦点数量与电离辐射造成的DSB数量存在对应关系[8-9]。DSB修复的主要通路包括同源重组修复(homologous recombination,HR)和非同源末端连接(non-homologous end joining,NHEJ),二者在损伤修复时涉及到多种信号通路。Rad51蛋白酶是HR的关键酶、损伤的感应器和周期检查点关键蛋白及体内催化同源重组性DNA修复最主要的关键酶[10]。因此,本研究通过建立稳定靶向沉默ATRX的HeLa细胞模型,并给予电离辐射,分别检测ATRX、γH2AX和RAD51蛋白表达以及γH2AX和RAD51焦点的形成,探讨ATRX参与辐射诱导HeLa细胞DNA损伤修复的作用,为肿瘤放射治疗提供新的理论和实验依据。

1 材料与方法 1.1 细胞、试剂和主要仪器

人宫颈癌HeLa细胞和293T细胞由本实验室保存。MEM培养基和胎牛血清(美国Gibco公司),HieffTransTM脂质体核酸转染试剂(上海翊圣生物科技有限公司),青链霉素(美国ThermoFisher scientific公司),GAPDH、ATRX、γH2AX和Rad51一抗(美国Santa Cruz公司),Red fluorescent抗兔二抗(美国CST公司),辣根过氧化物酶标记的二抗(美国Immunoway公司),嘌呤毒素puromycin(美国Sigma公司),其他试剂为国产。X射线辐照仪X-RAD 320iX(Precision X-ray,美国Inc公司),垂直板电泳系统(美国BioRad公司)。

1.2 靶向沉默ATRX的HeLa细胞的获得

靶向ATRX的3段sh RNA序列分别为5′-ATCCTCAAGAGGTTGAATC-3′、5′-TTTCTTATGTTCACCACCG-3′和5′-TTATCTTGTGGAACTTCCT-3′。分别构建到pGIPz载体上,即pGIPz-shATRX1、pGIPz-shATRX2和pGIPz-shATRX3,同时设立pGIPz-shControl为阴性对照,pSPAX2和pMD2G质粒(美国罗格斯大学肿瘤研究所沈智渊博士惠赠)。利用Hieff TransTM转染试剂将pGIPz-shControl、pGIPz-shATRX1、pGIPz-shATRX2和pGIPz-shATRX3与pSPAX2和pMD2G分别共转染293T细胞,Hieff TransTM:shRNA:pSPAX2:pMD2G=120 μL:3 μg:1.5 μg:1.5 μg。48和72 h收取上清液并利用0.45 μm滤膜过滤后加到培养于6孔板的HeLa细胞中,共感染2次。通过观察绿色荧光状态判定感染效率,并加入10 μL的puromycin进行阳性筛选,命名为shCon-HeLa、shA1-HeLa、shA2-HeLa和shA3-HeLa细胞,逐渐将阳性细胞扩大并冻存液氮中备用。

1.3 Western blotting法检测蛋白表达

分别将shCon-HeLa、shA1-HeLa、shA2-HeLa和shA3-HeLa细胞接种于6孔板,按照每孔1×107个细胞,24 h后收集细胞,并加入裂解液RIPA 100 μL,超声后加入5×loading buffer,100℃变性10 min后,冷却样品直接上样;取shCon-HeLa和shA1-HeLa组细胞进行2和8 Gy X射线照射,1、6和24 h后提取总蛋白;另取上述2组细胞进行4 Gy照射,0、0.5、1.0、3.0和6.0 h提取总蛋白;40 μg蛋白变性后上样,浓缩胶80 V,分离胶120 V,SDS-PAGE电泳后转膜缓冲液4℃中过夜湿转,5%脱脂奶粉封闭1 h后,ATRX一抗(TBST配置,1:1 000)、GAPDH、γH2AX和Rad51一抗(1:500),37℃孵育2 h,TBST洗3次,每次10 min,加入辣根过氧化物酶标记的二抗(TBST配置,1:3 000)后37℃孵育1 h,TBST洗3次,加入ECL液A和B,暗室中曝光,拍照分析。

1.4 免疫荧光技术检测γH2AX和Rad51焦点数

分别将shCon-HeLa和shA1-HeLa细胞接种于放置了盖玻片的6孔板,按照每孔1×105个细胞,12 h后采用4 Gy照射,照射后分别于0、0.5、1.0、3.0和6.0h采用4%多聚甲醛固定10 min,2%BSA + 0.3% TritonX100封闭液室温封闭1 h,γH2AX一抗和Rad51一抗(1:500)4℃过夜孵育,PBS洗5次,每次5 min,红色荧光二抗(1:1 000)室温孵育1 h,PBS洗5次,每次5 min,8 μL的DAPI滴加到载玻片上,将带有细胞的盖玻片放置在载玻片上进行封片。荧光显微镜下观察γH2AX和Rad51焦点形成(点状红色荧光所示),随机选取5个视野,每个视野选择20个细胞,计数焦点数。

1.5 统计学分析

采用SPSS 24.0统计软件进行统计学分析。γH2AX和Rad51焦点数以x±s表示,多组间样本均数比较采用单因素方差分析。以P < 0.05为差异有统计学意义。

2 结果 2.1 Western blotting法检测ATRX蛋白表达

shCon-HeLa细胞中可见ATRX蛋白表达,而shA1-HeLa、shA2-HeLa和shA3-HeLa细胞中无ATRX蛋白表达,表明靶向沉默ATRX的HeLa细胞模型构建成功。见图 1

Lane 1: shCon-HeLa cells; Lane 2: shA1-HeLa cells; Lane3: shA2-HeLa cells; Lane 4: shA3-HeLa cells. 图 1 Western blotting法检测4种细胞模型中ATRX蛋白表达电泳图 Fig. 1 Electrophoregram of ATRX protein expressions in 4 kinds of cell models measured by Western blotting method
2.2 2和8 GyX射线照射后ATRX蛋白表达

shCon-HeLa组和shA1-HeLa组细胞给予2和8 GyX射线照射,分别于1、6和24 h检测ATRX蛋白表达。2 Gy照射后,shCon-HeLa细胞中ATRX蛋白表达量随照射后时间延长明显增加,24 h时达到最大值;而8 Gy照射后,ATRX蛋白表达量一直处于较高水平。见图 2

图 2 2和8Gy X射线照射后1、6和24 h时ATRX蛋白表达电泳图 Fig. 2 Electrophoregramof ATRX protein expressions at 1, 6, and 24 h after 2 and 8 Gy X-ray irradiation
2.3 4 Gy照射后2组细胞中γH2AX和Rad51焦点数

荧光显微镜下观察4 Gy照射后shCon-HeLa组和shA1-HeLa组细胞中γH2AX和Rad51焦点形成:0~6.0 h时shCon-HeLa组和shA1-HeLa组细胞中γH2AX和Rad51焦点数均在1.0 h时最多,而后逐渐降低,与shCon-HeLa组比较,shA1-HeLa组细胞中γH2AX和Rad51焦点数在1.0和6.0 h均明显增多(P < 0.05或P < 0.01)。见表 1图 3(插页一)。

图 3 荧光显微镜观察4 Gy照射后0~6 h时2组细胞中γH2AX和Rad51焦点形成~ Fig. 3 Formation of γH2AX and Rad51 foci in cells in two groups 0-6 h after 4 Gy irradiation observed by fluorescence microscope
表 1 4 GyX射线照射后0~6.0 h 2组细胞中γH2AX和Rad51焦点数 Tab. 1 Number of γH2AX and Rad51 foci in cells in two groups at 0-6.0 h after 4 Gy X-ray irradiation
(n=100, x ±s)
Group γH2AX foci
(t/h) 0 0.5 1.0 3.0 6.0
shCon-HeLa 2.26±0.76 27.73±4.94 41.00±2.91 25.20±8.42 14.20±5.04
shA1-HeLa 2.31±0.35 28.80± 6.18 46.91±2.19* 29.73±6.64 23.40±5.65**
Group Rad51 foci
(t/h) 0 0.5 1.0 3.0 6.0
shCon-HeLa 2.12±0.93 7.03±1.57 16.27±3.60 17.37±3.76 6.50±1.61
shA1-HeLa 2.11±1.05 7.47±2.07 19.33±3.59* 19.23±3.48 18.16±4.96**
* P < 0.05, * * P < 0.01 compared with shCon-HeLa group.
2.4 4 Gy X射线照射后不同时间点γH2AX和Rad51蛋白表达

4 GyX射线照射后1.0和6.0 h,shA1-HeLa组细胞中Rad51和γH2AX蛋白表达量均高于shCon-HeLa组,与γH2AX和Rad51焦点数的变化规律基本一致。见图 4

Lane1: shCon-HeLagroup; Lane 2: shA1-HeLa group. 图 4 Western blotting法检测4 Gy X射线照射后不同时间点γH2AX和Rad51蛋白表达电泳图 Fig. 4 Electrophoregram of expressions of γH2AX and Rad51 proteins at different time points after 4 Gy X-ray irradiation detected by Western blotting method
3 讨论

DNA损伤修复涉及非常多的基因,ATRX基因是一种重要的DNA损伤修复基因,其主要功能包括维持端粒的稳定、染色体黏附、维持DNA结构和直接连接到双链断裂位点等[11-14]。放射治疗杀伤肿瘤细胞的基本机制是DNA的损伤修复反应,因放射治疗会造成基因组DNA的DSB,导致细胞DNA损伤后得不到正确的修复,引起细胞发生凋亡,进而使细胞丧失增殖能力[15]。本研究利用靶向ATRX基因的慢病毒shRNA表达载体,转染293T细胞后,利用慢病毒2次感染宫颈癌HeLa细胞,并经puromycin阳性筛选获得稳定ATRX沉默的细胞模型,Western blotting法检测结果显示:3条靶向ATRX的序列具有较好的沉默效果,均可作为候选细胞进行后续研究,故选取shCon-HeLa和shA1-HeLa细胞进行后续研究。电离辐射作为一种高能物理损伤因素,可以通过直接或间接作用引起受照射生物组织和细胞的损伤。在分子水平上,无论是辐射的直接作用还是间接作用产生的自由基和生物大分子(脂质、蛋白质、DNA和RNA等)均是辐射的直接效应靶点。在生命进程中,DNA难免会受到源于外界环境中有害的化学物质、紫外线以及射线等威胁,所造成的DNA损伤也是正常细胞转变为肿瘤细胞的主要诱因之一。电离辐射产生的DNA损伤穿透力强,不受亚细胞结构的影响,发生速度极快,而且损伤的形式多样,包含碱基和核苷酸水平的损伤以及链损伤。辐射导致的DNA损伤包括SSB和DSB、碱基损伤和DNA-蛋白交联[16-17]。DSB是辐射后严重的损伤,主要通过HR和NHEJ修复[18-19]。2和8 Gy照射后,shCon-HeLa细胞中ATRX蛋白表达量明显增加,提示其参与辐射导致的DNA损伤修复。γH2AX和Rad51焦点及蛋白表达均可作为DSB修复的标志[8-10],因此本实验检测二者焦点数及蛋白表达,以反映辐射后DNA损伤修复的状态。4 Gy X射线照射后shCon-HeLa和shA1-HeLa细胞中γH2AX和Rad51焦点数均迅速增高,在1 h时达到最大值,至6 h时逐渐降低,但仍高于0 h;与shCon-HeLa组比较,shA1-HeLa组细胞中γH2AX和Rad51焦点数均明显升高,提示缺失ATRX基因后,HR修复能力降低,ATRX参与DNA损伤后的HR修复。采用Western blotting法检测2种蛋白表达结果显示:在2种细胞间存在γH2AX和Rad51蛋白表达的差异,与焦点形成数的规律基本一致。上述结果显示:辐射损伤DNA后ATRX参与双链断裂的修复,是一个重要的HR修复的参与者。

综上所述,本研究利用靶向ATRX的慢病毒实现了沉默HeLa细胞中ATRX的目的,经过电离辐射后,对照组ATRX具有辐射增强表达的特性,且对照组和缺失ATRX的HeLa细胞中γH2AX和Rad51焦点数增加,随时间延长对照组逐渐回落,而缺失ATRX的HeLa细胞中焦点数降低则较慢,且蛋白表达的结果与其相似,提示缺失ATRX后细胞修复能力降低。以ATRX为靶点的肿瘤基因-放射治疗为临床放射治疗提供了新的理论和实验数据。

参考文献
[1] MITSON M, KELLEY L A, STERNBERG M J, et al. Functional significance of mutations in the Snf2 domain of ATRX[J]. Hum Mol Genet, 2011, 20(13): 2603–2610. DOI:10.1093/hmg/ddr163
[2] KOSCHMANN C, CALINESCU A A, NUNEZ F J, et al. ATRX loss promotes tumor growth and impairs nonhomologous end joining DNA repair in glioma[J]. Sci Transl Med, 2016, 8(328): 328ra28. DOI:10.1126/scitranslmed.aac8228
[3] LAW M J, LOWER K M, VOON H P, et al. ATR-X syndrome protein targets tandem repeats and I nfluences allele-specific expression in a size-dependent manner[J]. Cell, 2010, 143(3): 367–378. DOI:10.1016/j.cell.2010.09.023
[4] DUC C, BENOIT M, DÉTOURN G, et al. Arabidopsis ATRX modulates H3.3 occupancy and fine-tunes gene expression[J]. Plant Cell, 2017, 29(7): 1773–1793. DOI:10.1105/tpc.16.00877
[5] MUKHERJEE J, JOHANNESSEN T C, OHBA S, et al. Mutant IDH1 cooperates with ATRX loss to drive the alternative lengthening of telomere phenotype in glioma[J]. Cancer Res, 2018, 78(11): 2966–2977. DOI:10.1158/0008-5472.CAN-17-2269
[6] VUONG H G, TRAN T T K, NGO H T T, et al. Prognostic significance of genetic biomarkers in isocitrate dehydrogenase-wild-type lower-grade glioma:the need to further stratify this tumor entity-a meta-analysis[J]. Eur J Neurol, 2019, 26(3): 379–387. DOI:10.1111/ene.13826
[7] 龚守良. 医学放射生物学[M]. 4版.北京: 中国原子能出版社,2015.
[8] KUEFNER M A, BRAND M, ENGERT C, et al. Radiation induced DNA double-strand breaks in radiology[J]. Rofo, 2015, 187(10): 872–878. DOI:10.1055/s-0035-1553209
[9] CAMERO S, CECCARELLI S, DE FELICE F, et al. PARP inhibitors affect growth, survival and radiation susceptibility of human alveolar and embryonal rhabdomyosarcoma cell lines[J]. J Cancer Res Clin Oncol, 2019, 145(1): 137–152. DOI:10.1007/s00432-018-2774-6
[10] LILLIAN C D, SALAHUDDIN S, KRISTINA H S. Sgs1 binding to Rad51 stimulates homology-directed DNA repair in Saccharomyces cerevisiae[J]. Genetics, 2018, 208(1): 125–138. DOI:10.1534/genetics.117.300545
[11] VOON H P, HUGHES J R, RODE C, et al. ATRX plays a key role in maintaining silencing at interstitial heterochromatic loci and imprinted genes[J]. Cell Rep, 2015, 11(3): 405–418. DOI:10.1016/j.celrep.2015.03.036
[12] NOH K M, MAZE I, ZHAO D, et al. ATRX tolerates activity-dependent histone H3 methyl/phos switching to maintain repetitive element silencing in neurons[J]. Proc Natl Acad Sci U S A, 2015, 112(22): 6820–6827. DOI:10.1073/pnas.1411258112
[13] DE LA FUENTE R, BAUMANN C, VIVEIROS M M. Chromatin structure and ATRX function in mouse oocytes[J]. Results Probl Cell Differ, 2012, 55: 45–68.
[14] RATNAKUMAR K, BERNSTEIN E. ATRX:the case of a peculiar chromatin remodeler[J]. Epigenetics, 2013, 8(1): 3–9.
[15] LUO J, SI Z Z, LI T, et al. MicroRNA-146a-5p enhances radiosensitivity in hepatocellular carcinoma through replication protein A3 induced activation of the DNA repair pathway[J]. Am J Physiol Cell Physiol, 2019, 316(3): C299–C311. DOI:10.1152/ajpcell.00189.2018
[16] NAKANO T, XU X, SALEM A M H, et al. Radiation-induced DNA-protein cross-links:Mechanisms and biological significance[J]. Free Radic Biol Med, 2017, 107: 136–145. DOI:10.1016/j.freeradbiomed.2016.11.041
[17] SAGE E, SHIKAZONO N. Radiation-induced clustered DNA lesions:Repair and mutagenesis[J]. Free Radic Biol Med, 2017, 107: 125–135. DOI:10.1016/j.freeradbiomed.2016.12.008
[18] 赵忆宁, 何颖, 沈先荣, 等. 西咪替丁对低剂量电离辐射致大鼠氧化应激的保护作用[J]. 解放军医学杂志, 2017, 42(2): 128–133.
[19] CECCALDI R, RONDINELLI B, D'ANDREA A D. Repair pathway choices and consequences at the double-strand break[J]. Trends Cell Biol, 2016, 26(1): 52–64. DOI:10.1016/j.tcb.2015.07.009