Oxidative DNA damage-induced tumorigenesis and its avoidance mechanism

DNA氧化损伤诱导肿瘤发生及其避免机制

基本信息

批准号：
12213098
负责人：
TSUZUKI Teruhisa
金额：
$ 49.66万
依托单位：
Kyushu University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research on Priority Areas
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2004
项目状态：
已结题

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 the most abundant, and appears to play important roles in mutagenesis and carcinogenesis. Studies with Escherichia coli mutator mutants revealed that organisms possess elaborate mechanisms that prevent mutations caused by oxidation of the guanine base, in both DNA and free nucleotide forms. Enzymatic activities which may be responsible for preventing 8-oxoG-evoked mutations were identified in mammalian cells. We have focused on following the two enzymes. MTH1 (Mthl) protein is the mammalian counterpart of E. coli MutT protein, which hydrolyzes 8-oxo-dGTP to monophosphate in the nucleotide pool, thereby preventing occurrence of transversion mutations. On the other hand, MUTYH (Mutyh) protein, a counterpart of E. coli MutY protein, having adenine/2-hydroxyadeni … More ne DNA glycosylase activity, is expected to prevent G : C to T : A transversions, by excising adenine from G : A mismatches induced by 8-oxoG and 2-OH-A. To analyze the function of the mammalian Mthl and Mutyh proteins in vivo, we established gene-knockout mice for these two enzymes by gene targeting, and investigated spontaneous tumorigenesis as well as mutagenesis.When examined 18 months after birth, a greater number of tumors were formed in the lungs, livers of Mthl-deficient mice, as compared with wild-type mice (Tsuzuki, T. et al., 2001). Mutation frequencies on the rpsL transgene in spleen samples recovered at the age of 4 and 24 weeks, were determined. The spontaneous mutation frequency observed in spleen samples from Mthl-deficient mice showed no dramatic increase compared to the value of the one in wild-type mice. The site distribution of the mutations occurred on rpsL gene was slightly different between these to Mthl genotypes in spleen samples. In Mthl-deficient mice, there are 1-basepair frameshift mutations at the mononucleotide repeats those were not found in wild-type mice (Egashira, A. et al., 2002). When examined 18 months after birth, a greater number of tumors had formed in various tissues of Mutyh-deficient mice, as compared with wild-type mice. Especially, more small intestinal tumors were formed in Mutyh-deficient mice than in wild-type mice (in preparation). Mutation frequency observed in spleen samples from the Mutyh-deficient mice, at the age of 24 weeks, showed no apparent increase compared to the value of samples from wild-type mice. However, the site distribution of the mutations that occurred in the rpsL gene was significantly different between these two Mutyh genotypes ; an increase in frequency of G : C to T : A transversions was evident in Mutyh nullizygous mice (in preparation).Thus, both the Mthl-and Mutyh-deficient mice will provide useful models for investigating the roles of oxidative stress in human health. Less

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-氧-7,8-二氢甘氨酸（8-oxog）是最丰富的，并且似乎在诱变和致癌作用中起着重要作用。对大肠杆菌突变体突变体的研究表明，生物具有精致的机制，可防止DNA和游离核苷酸形式中鸟嘌呤碱基氧化引起的突变。在哺乳动物细胞中鉴定出可能导致预防8-oxog诱发突变的酶促活性。我们专注于遵循两个酶。 MTH1（MTHL）蛋白是大肠杆菌Mutt蛋白的哺乳动物对应物，该蛋白将8-氧-DGTP水解为核苷酸池中的单磷酸盐，从而防止发生转移突变。另一方面，具有腺嘌呤/2-羟基二烯的大肠杆菌蛋白质的Mutyh（mutyh）蛋白质……更多的DNA糖基酶活性，预计会防止G：C至T：A t t t transessions，通过从G：8-氧基诱导的MiSmatches中的腺嘌呤从G：A t transce t：A transess。 To analyze the function of the mammalian Mthl and Mutyh proteins in vivo, we established gene-knockout mice for these two enzymes by gene targeting, and investigated sponsoreous tumorigenesis as well as mutagenesis.When examined 18 months after birth, a greater number of tumors were formed in the lungs, lives of Mthl-deficient mice, as compared with wild-type mice （Tsuzuki，T。等，2001）。确定了在4和24周时恢复的Sleen样品中RPSL变换上的突变频率。与野生型小鼠的值相比，来自MTHL缺乏小鼠的卵形样品中观察到的赞助突变频率没有显着增加。突变的位点分布发生在RPSL基因上，它们之间在脾样品中与MTHL基因型之间的分布略有不同。在MTHL缺陷小鼠中，单核苷酸重复有1-Basepair的移码突变，这些突变在野生型小鼠中未发现这些突变（Egashira，A。et al。，2002）。与野生型小鼠相比，在出生后18个月检查时，在MutyH缺陷型小鼠的各种时间内形成了更多的肿瘤。特别是，在缺乏Mutyh的小鼠中形成的小肠道肿瘤比野生型小鼠（准备）中形成更多的小肠道肿瘤。与野生型小鼠的样品相比，在24周的脾脏中观察到的突变频率在24周的脾样品中观察到没有明显增加。但是，这两种mutyh基因型之间发生的突变的位点分布显着差异。 g：c至t的频率增加：在mutyh nullizygous小鼠中证明了横向的频率（在制备中）。因此，MTHL和MUTYH缺陷小鼠均可为研究氧化应激在人类健康中的作用提供有用的模型。较少的