CONTRIBUTION OF O-6-ALKYLGUANINE AND N-ALKYLPURINES TO THE FORMATION OF SISTER-CHROMATID EXCHANGES, CHROMOSOMAL-ABERRATIONS, AND GENE-MUTATIONS - NEW INSIGHTS GAINED FROM STUDIES OF GENETICALLY-ENGINEERED MAMMALIAN-CELL LINES
CONTRIBUTION OF O-6-ALKYLGUANINE AND N-ALKYLPURINES TO THE FORMATION OF SISTER-CHROMATID EXCHANGES, CHROMOSOMAL-ABERRATIONS, AND GENE-MUTATIONS - NEW INSIGHTS GAINED FROM STUDIES OF GENETICALLY-ENGINEERED MAMMALIAN-CELL LINES
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DOI：
10.1002/em.2850220418
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发表时间：
1993-01-01
影响因子：
2.8
通讯作者：
COQUERELLE, T
中科院分区：
文献类型：
--
作者：
KAINA, B;FRITZ, G;COQUERELLE, T
O-6-甲基-和O-6-乙基鸟嘌呤是单官能烷化剂在DNA中诱导的主要诱变前和致癌前病变，尽管形成量很少。这些病变在 SCE 和像差形成中的参与尚不清楚。我们分析了 O-6-烷基鸟嘌呤对 SCE 和畸变形成的贡献，以及其在表达不同量的人 O-6-甲基鸟嘌呤-DNA 甲基转移酶 (MGMT) 的转基因中国仓鼠卵巢 (CHO) 细胞系中的毒性和点突变诱导作用。与 MGMT 缺陷细胞相比，过度表达 MGMT（或细菌 Ada 蛋白）的细胞获得了对烷基化诱导的 SCE 和畸变形成的抵抗力。 SCE 的保护水平和细胞杀伤之间存在明显的相关性，表明这两种现象是相互关联的。保护作用取决于 MGMT 表达水平、用于烷基化的试剂以及细胞周期进程。我们的数据表明，至少有两种病变导致 SCE 和畸变形成，即 O-6-烷基鸟嘌呤和一种或多种 N-烷基化产物。对于 SCE，O-6-甲基鸟嘌呤转化为细胞遗传学效应的概率估计约为 1:30，对于治疗后第一次和第二次有丝分裂中的染色体畸变，其概率分别约为 1:147,000 和 1:22,000。 SCE 的诱导以及 O-6-甲基鸟嘌呤的畸变可能也需要两个复制周期，并且应该涉及次级 DNA 损伤的形成。转染人 MPG-cDNA 后，过表达 N-甲基嘌呤-DNA 糖基化酶 (MPG) 的 CHO 细胞中 3-甲基腺嘌呤和 7-甲基鸟嘌呤的修复增强，但并未产生针对甲基化诱导的 SCE 和畸变的保护作用，可能是因为切除修复不完全。 MPG 过表达细胞对甲基化剂的反应更加敏感，表明 MPG 作用形成的无嘌呤位点是 SCE 和畸变诱导病变。 (C) 1993 Wiley-Liss, Inc.
O-6-methyl- and O-6-ethylguanine are the major premutagenic and precarcinogenic lesions induced in DNA by monofunctional alkylating agents, albeit formed in minor amounts. The involvement of these lesions in SCE and aberration formation is less clear. We have analyzed the contribution of O-6-alkylguanine to SCE and aberration formation, as well as its toxic and point mutation inducing effect in transgenic Chinese hamster ovary (CHO) cell lines that express variable amounts of human O-6-methylguanine-DNA methyltransferase (MGMT). Cells that overexpress MGMT (or the bacterial Ada protein) gained resistance to the formation of alkylation-induced SCEs and aberrations, as compared to MGMT deficient cells. A correlation was apparent between the level of protection for SCEs and cell killing, indicating that both phenomena are interrelated. The protective effects were dependent on the level of MGMT expression, the agent used for alkylation, and cell cycle progression. Our data suggest that at least 2 kinds of lesions are responsible for SCE and aberration formation, namely, O-6-alkylguanine and one or various N-alkylation products. The probability that O-6-methylguanine is converted into cytogenetic effects has been estimated to be about 1:30 for SCEs, and 1:147,000 and 1:22,000 for chromosomal aberrations in the first and second post-treatment mitosis, respectively. The induction of SCEs and likely also of aberrations by O-6-methylguanine requires two replication cycles and is supposed to involve the formation of secondary DNA lesions. Increased repair of 3-methyladenine and 7-methylguanine in CHO cells that overexpress the N-methylpurine-DNA glycosylase (MPG) after transfection with the human MPG-cDNA did not give rise to protection against methylation-induced SCEs and aberrations, probably because of incomplete excision repair. MPG overexpressing cells reacted even more sensitively to methylating agents, suggesting apurinic sites formed as a result of MPG action to be SCE and aberration-inducing lesions. (C) 1993 Wiley-Liss, Inc.