作者：赵洁，董子明，毛海洲，王煊，赵国强

【关键词】  ,DNA聚合酶β

    Mutation characteristics of DNA polymerase beta gene in human gastric carcinoma tissue

　　【Abstract】 AIM: To detect the mutation characteristics of DNA polymerase beta gene (polβ gene) in human gastric carcinoma. METHODS:  Total RNA was extracted from 32 gastric cancer samples and 32 tissue samples adjacent to tumors. The RTPCR was carried out and the PCR product was cloned and sequenced with Sangers method subsequently. RESULTS:  Three from the seven abnormal SSCP samples were sequenced and the mutation sites were: site 196 A→G, site 268 A→G and site 790 A→T. No mutation was found by sequencing in a normal PCRSSCP sample of the tissues adjacent to the tumor. Omiga analysis showed that the three point mutations led to changes of amino acid: site 196 A→G of nuclEic acid resulted in site 28 Asn→Ser of amino acid, site 268 A→G of nucleic acid resulted in site 52 Lys→Arg of amino acid, and site 790 A→T of nucleic acid resulted in site 226 Asp→Val of amino acid. Choufasman method of Dnasis showed that site 196 A→G mutation caused great changes in the secondary structure of polβenzyme. CONCLUSION:  The polβgene mutation rate is up to 21.9%. The three point mutations observed in this study all lead to the alternation of amino acid. Site 196 A→G mutation can cause great changes in the secondary structure of polβ enzyme.

　　【Keywords】 DNA polymerase beta; gene mutation; stomach neoplasms

　　【摘要】 目的：探讨人胃癌DNA聚合酶β(polβ)基因突变的特点. 方法 ：对32例人胃癌组织及32例正常对照组织中提取总RNA，进行RTPCR，SSCP，对PCR产物克隆后以Sangers法测序，并采用Omiga及Dansis软件 分析 结果. 结果：人胃癌标本的polβ基因突变率21.9%. 测序分析了7例SSCP异常中的3例，其突变分别为196位A→G，268位A→G，790位A→T；经OMIGA软件分析，这3个polβ的点突变均导致了氨基酸的改变，具体形式为：核酸196位A→G导致氨基酸28位Asn→Ser；核酸268位A→G导致氨基酸52位Lys→Arg；核酸790位A→T导致氨基酸226位Asp→Val. DNASIS软件Choufasman算法推测，polβ的196位A→G突变可以导致polβ酶蛋白的二级结构图明显改变. 结论：人胃癌组织polβ基因突变率达21.9%；这3个polβ的点突变都导致了氨基酸的改变，196位A→G突变可以导致polβ酶蛋白的二级结构明显改变.

　　【关键词】 DNA聚合酶β；基因突变；胃肿瘤