Mechanisms for control of spontaneous mutagenesis as revealed by the use gene-targeted mice

通过使用基因靶向小鼠揭示的控制自发突变的机制

基本信息

批准号：
11440222
负责人：
SEKIGUCHI Mutsuo
金额：
$ 9.02万
依托单位：
Fukuoka Dental College
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-11440222/
关键词：
spontaneous mutagenesis DNA replication DNA repair enzyme apoptosis Oxidized guanine methylated bases active oxygen species carcinogenesis 発がん遺伝子障害大腸菌 MTH1

项目摘要

Oxygen radicals, which can be produced through normal cellular metabolism, are thought to play an important role in mutagenesis and tumorigenesis. Among various classes of oxidative DNA damage, 8-oxo-7, 8-dihydroguanine(8-oxoG) is most important because of its abundance and mutagenicity. The MTH1 gene encodes an enzyme that hydrolyzes 8-oxo-dGTP to monophosphate in the nucleotide pool, thereby preventing occurrence of transversion mutations. By means of gene targeting, we have established MTH1 gene-Bknockout cell lines and mice. When examined 18 months after birth, a greater number of tumors were formed in the Rmgs, livers, and stomachs of MTH1-deficient mice, as compared with wild-type mice. The MTH1-deficient mouse will provide a useful model for investigating the role of the MH1 protein in normal conditions and under oxidative stress. Alkylation of DNA at the o^6-position of guanine is one of the most critical events leading to mutation, cancer, and cell death. The enzyme o^6-methylguanine-DNA methyltransferase repairs o^6-methylguanine as well as a minor methylated base, o^4-methylthymine, in DNA. Mouse lines deficient in the methyltransferase (MGMT) gene are hypersensitive to both the killing and to the tumorigenic effects of alkylating agents. We now show that these dual effects of an alkylating agent can be dissociated by introduction of an additional defect in mismatch repair. Mice with mutations in both alleles of the MGMT gene and one of the mismatch repair genes, MLH1, are as resistant to methylnitrosourea (MNU) as are wild-type mice, in terms of survival, but do have numerous tumors after receiving MNU. In contrast to MGMT^<-/-> MLH1^<+/+> mice with decrease in size of the thymus and hypocellular bone marrow after MNU administration no conspicuous change was found in MGMT^<-/-> MLH1^<+/+> mice treated in the same manner. Thus, killing and tumorigenic effects of an alkylating agent can be dissociated by preventing mismatch repair pathways.

可以通过正常细胞代谢产生的氧自由基在诱变和肿瘤发生中起着重要作用。在各种类别的氧化DNA损伤中，8-oxo-7，8-二氢甘油氨酸（8-oxog）最重要，因为它的丰度和诱变。 MTH1基因编码一种将8-氧-DGTP水解为核苷酸池中的单磷酸的酶，从而防止发生横向突变。通过基因靶向，我们已经建立了MTH1基因 - 基因细胞系和小鼠。与野生型小鼠相比，在出生后18个月检查出生后，在MTH1缺陷型小鼠的RMG，肝脏和胃中形成了更多肿瘤。缺乏MTH1的小鼠将为研究MH1蛋白在正常条件和氧化应激下的作用提供有用的模型。 DNA在鸟嘌呤的O^6位置的烷基化是导致突变，癌症和细胞死亡的最关键事件之一。 DNA中的酶O^6-甲基鸟嘌呤-DNA甲基转移酶修复O^6-甲基鸟嘌呤以及少量的甲基化碱，O^4-甲基胰胸腺素。甲基转移酶（MGMT）基因缺乏的小鼠系对烷基化剂的杀伤和致瘤作用都过敏。现在，我们表明，通过引入不匹配维修中的其他缺陷，可以解散烷基化剂的这些双重效应。在MGMT基因的等位基因和一个不匹配修复基因MLH1中的突变的小鼠MLH1均与野生型小鼠一样对甲基硝基苯甲酸（MNU）的抗性，但就生存而言，野生型小鼠也是如此，但在接受MNU后确实有许多肿瘤。与MGMT^< - / - > MLH1^<+/+>小鼠相比，在MNU给药后，胸腺大小降低和胸骨骨髓的大小降低，在MNU给药后未发现MGMT^< - > MLH1^<+/+>小鼠的明显变化。因此，烷基化剂的杀伤和致瘤作用可以通过防止不匹配的修复途径解离。