Preferential DNA damage and poor repair determine ras gene mutational hotspot in human cancer.
Preferential DNA damage and poor repair determine ras gene mutational hotspot in human cancer.
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DOI：
10.1093/jnci/94.20.1527
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发表时间：
2002-10
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影响因子：
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通讯作者：
Zhaohui Feng;Wenwei Hu;James X. Chen;A. Pao;Haiying Li;W. Rom;M. Hung;M. Tang
中科院分区：
文献类型：
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作者：
Zhaohui Feng;Wenwei Hu;James X. Chen;A. Pao;Haiying Li;W. Rom;M. Hung;M. Tang
背景技术ras基因的突变常见于人类癌症和动物模型中。虽然H-、N-和K-ras基因的密码子12、13和61的突变可以激活其致癌功能，但K-ras的密码子12的突变是人类癌症中三个ras基因中最常见的突变。为了研究人 K-ras 的密码子 12 是否对致癌物特别敏感和/或该密码子处的致癌物-DNA 加合物修复效率是否较低，我们检测了烟草烟雾致癌物在正常人支气管上皮和成纤维细胞中诱导的 DNA 损伤。方法我们使用 UvrABC 核酸酶切开法结合连接介导的聚合酶链式反应，绘制了 H-ras、N-ras 和 K-ras 外显子 1 和 2 内由苯并[a]芘二醇环氧化物 (BPDE) 和其他大致癌物诱导的 DNA 加合物的分布图。我们还使用相同的方法分析了这三个基因中的 BPDE-DNA 加合物修复效率。结果 K-ras 基因的密码子 12 和 14 是致癌物-DNA 加合物形成的热点，而密码子 13 和 61 分别很少或没有加合物形成。在密码子 14 处形成的 BPDE-DNA 加合物的修复速度几乎是在密码子 12 处形成的两倍。在 H-ras 和 N-ras 的密码子 12 处有一些 BPDE-DNA 加合物形成，但该密码子不是热点。此外，在 H-ras 或 N-ras 基因中，密码子 12 和其他分析的密码子（密码子 3 和 18）之间的修复率没有观察到显着差异。结论 这些发现将人类癌症 K-ras 密码子 12 处的突变热点与优先 DNA 损伤和修复不良联系起来。
BACKGROUND Mutations in ras genes are commonly found in human cancers and in animal models. Although mutations at codons 12, 13, and 61 of H-, N- and K-ras genes can activate their oncogenic function, mutations at codon 12 of K-ras are the most common mutations found among the three ras genes in human cancers. To investigate whether codon 12 of human K-ras is especially susceptible to carcinogens and/or whether carcinogen-DNA adducts at this codon are repaired less efficiently, we examined tobacco smoke carcinogen-induced DNA damage in normal human bronchial epithelial and fibroblast cells. METHODS We used the UvrABC nuclease incision method in combination with ligation-mediated polymerase chain reaction to map the distribution of DNA adducts induced by benzo[a]pyrene diol epoxide (BPDE) and other bulky carcinogens within exons 1 and 2 in H-ras, N-ras, and K-ras. We also analyzed BPDE-DNA adduct repair efficiency in these three genes using the same method. RESULTS Codons 12 and 14 of the K-ras gene were hotspots for carcinogen-DNA adduct formation, with little and no adduct formation at codons 13 and 61, respectively. The BPDE-DNA adducts formed at codon 14 were repaired almost twice as quickly as those formed at codon 12. There was some BPDE-DNA adduct formation at codons 12 of H-ras and N-ras, but this codon was not a hotspot. Furthermore, no substantial difference in repair rates between codon 12 and the other codons analyzed (codons 3 and 18) was observed in either the H-ras or N-ras genes. CONCLUSION These findings link the human cancer mutational hotspot at codon 12 of K-ras to preferential DNA damage and poor repair.