DNA MODIFICATION IN CARCINOGENESIS AND MUTATION

目前的证据表明，在建立赡养费方面的错误 基因组甲基化模式导致异位基因失活 重新激活。这些错误很可能涉及到某些人类 疾病；对于肿瘤尤其如此，其生长依赖于 幽默抑制基因的失活。在培养的细胞中，异位 甲基化和实际突变分别导致大约 所有基因失活的案例中有一半，而我们使特定的 预测人类肿瘤的某些部分将表现出失活的 肿瘤抑制基因的异位甲基化。此外，还有非常多的 酶介导的M5C转化为T和C转化为T的耐人寻味的证据 这些突变通常有助于癌症的发生和遗传 疾病。将使用生化和遗传手段来检测DNA 裂解物中的胞嘧啶脱氨酶和DNA 5-甲基胞嘧啶脱氨酶 哺乳动物细胞的。转甲基化反应的化学 提示DNA甲基转移酶应作为DNA胞嘧啶 脱氨酶在没有S-腺苷L-蛋氨酸的情况下的预测 也将接受测试。 特定于序列的甲基化模式在 配子发生和早期发育。特定于序列的错误 甲基化可能会导致发育缺陷，而且很脆弱 X综合征和亨廷顿氏病可能与DNA缺陷有关 甲基化。由于对序列的规则一无所知- 特定的从头开始甲基化，建议进行的实验将 确定序列特异性从头开始甲基转移酶是否 处于发育阶段，甲基化模式是 正在经历快速变化的。这些实验将使用一种非常敏感的 和DNA(胞嘧啶-5)-甲基转移酶的特异性通用探针 基于自杀底物5-氟-2‘-脱氧胞苷。这个 已知形式的DNA的特异性和其他功能 乙基转移酶将在现有的突变细胞系中进行研究 允许选择DNA乙基转移酶的活性突变体。这 提案描述了研究DNA作用的实验方法 在致癌和遗传病方面的修饰。

Current evidence suggest that errors in the establishment of maintenance of genomic methylation patterns contribute to ectopic gene inactivation of reactivation. These errors are likely to be involved in certain human diseases; this is especially true to tumors, whose growth depends on the inactivation of humor suppressor genes. In cultured cells, ectopic methylation and actual mutations are each responsible for approximately half of all cases of gene inactivation, and we make the specific prediction that some portion of human tumors will show inactivation of tumor suppressor genes by ectopic methylation. Also, there exists very intriguing evidence for enzyme-mediated conversion of m5C to T and C to U; these mutations commonly contribute to carcinogenesis and genetic disease. Biochemical and genetic means will be used to test for DNA cytosine deaminases and for DNA 5-methylcytosine deaminases in lysates of mammalian cells. The chemistry of the transmethylation reaction suggests that DNA Methyltransferase should act as a DNA cytosine deaminase in the absence of S-adenosyl L-methionine, and this prediction will also be tested. Sequence-specific methylation patterns are established during gametogenesis and early development. Errors in sequence-specific methylation can be expected to cause developmental defects, and Fragile X syndrome and perhaps Huntington's disease involve defective DNA methylation. Since nothing is known of the regulation of sequence- specific de novo methylation, experiments are proposed that will determine whether sequence-specific de novo methyltransferases are present at developmental stages where methylation patterns are undergoing rapid changes. These experiments will use a very sensitive and specific universal probe for DNA (cytosine-5)-methyltransferases based on the suicide substrate 5-fluoro 2'-deoxycytidine. The specificity and other functions of the known form of DNA Nethyltransferase will be studied in existing mutant cell lines which allow the selection of active mutants of DNA Nethyltransferase. This proposal describes experimental approaches to the role of DNA modification in carcinogenesis and genetic disease.