脑胶质瘤组织中DNA聚合酶β基因突变检测

Detection of DNA polymerase β gene mutation in human gliomas tissue

目的:研究人脑胶质瘤组织中DNA聚合酶β基因(polβ)的突变情况。方法:应用RT-PCR及SSCP检测22例脑胶质瘤、4例脑膜瘤、3例垂体瘤及1例肺部转移性鳞癌标本中polβ的表达,利用DNASIS、OMIGA软件及Chou&Fasman算法对扩增产物进行序列分析及蛋白质二、三级结构分析。结果:脑胶质瘤组织中DNApolβ突变率为6/22,共8个突变位点,2例发生504位A→G(131位Lys→Glu)、748位A→G(212位His→Arg)突变,2者蛋白质二级结构亦明显改变;598位T→C(162位Val→Ala)突变2例,但2者蛋白质二级结构无明显改变;2例Ⅲ级星形细胞瘤分别有2个和3个突变位点,但其各有1个相应的氨基酸未发生变异。Ⅱ级以下脑胶质瘤及脑膜瘤、垂体瘤等良性脑肿瘤组织均未发现DNApolβ基因突变。1例肺癌脑部转移性鳞状细胞癌DNApolβ基因出现5个突变位点,737位A→C(208位Pro未变异)、744位T→G(211位Lue→Val)、830位C→G(239位Cys→Trp)、866位A→C(251位Pro未变异)、870位A→C(253位Arg未变异),但蛋白质二级结构未改变。蛋白质三维结构图显示脑胶质瘤组织中6个氨基酸变异位点中,5个位于掌部,1个位于拇指部。结论:脑胶质瘤细胞中存在DNApolβ基因突变,且这些突变位点均为DNApolβ基因(尤其是掌部)活化结构域。提示脑胶质瘤的发生和发展可能与DNApolβ基因突变有关。

Aim: To detect DNA polymerase β gene (polβ) mutation in human gliomas tissue. Methods: DNA polβ gene in 30 cases of human brain carcinoma including 22 cases of gliomas,7 cases of benign tumors and 1 case of metastasizing sequamous cell carcinoma from lungs were examined using RT-PCR and SSCP.Sequence analysis was conducted using DNASIS and OMIGA softwares,and the second and third structure of the protein was assessed using Chou and Fasman method. Results: The mutation rate in gliomas was 27.3%(6/22), and the 8 mutation sites were found as follows: 504 nt A→G(131 Lys→Glu),748 nt A→G(212 His→Arg) in 2 case of gliomas, which resulted in the changes of protein secondary structure;598 nt T→C (162 Val→Ala) in 2 cases;776 nt T→C(221 Val→Val), and 915 nt G→A (268 Gly→Ser) in 1 case. 511 nt A→G (133 Asn→Ser), 586 nt T→C (158 Met→Thr), 854 nt A→G (247 Glu→Glu) in 1 case of oligodendroglial tumor. The protein secondary structure diagram had no change in the above 4 cases. Gene mutation was not observed in gliomas under Ⅱ grade and benign tumors. There were 5 sites of DNA polβ gene mutation in metastasizing sequamous cell carcinoma: 737 nt A→C(208 Pro→Pro), 744 nt T→G(211 Lue→Val), 830 nt C→G(239 Cys→Trp), 866 nt A→C(251 Pro→Pro),870 nt A→C(253 Arg→Arg).The protein secondary structure,the structure diagrams of the protein in three dimensions showed that 5 out of 6 mutation sites in gliomas tissue were located in the palm domain,and the other 1 at the thumb domain of the DNA polβ. Conclusion: There is mutation of DNA polβ gene in human galiomas tissue, which locates in the active domains(especially in the palm domain). It is suggested that the genesis and development of galiomas may be related to the mutation of DNA polβ gene.