Cytotoxic and mutagenic responses to X-rays and chemical mutagens in normal and p53-mutated human lymphoblastoid cells
Cytotoxic and mutagenic responses to X-rays and chemical mutagens in normal and p53-mutated human lymphoblastoid cells
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DOI：
10.1016/s0027-5107(96)00223-0
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发表时间：
1997-03-04
影响因子：
2.3
通讯作者：
Sofuni, T
中科院分区：
文献类型：
--
作者：
Honma, M;Hayashi, M;Sofuni, T
为了研究p53作为基因组守护者的作用，我们比较了正常（TK6）和p53突变（WTK-1）细胞对诱变剂的致突变性和细胞毒性反应。在这些细胞中发生的突变的特征也被检查。人淋巴母细胞系TK6和WTK-1来源于同一祖细胞系，但WTK-1细胞具有纯合子p53突变，导致p53突变蛋白过量产生。TK6和WTK-1细胞杂合胸苷激酶（tk）位点的自发突变频率分别为3.5 × 10（-6）和101.1 × 10（-6）。WTK-1细胞比TK6细胞耐药细胞毒性损伤的x射线,乙显示(EMS)和甲基显示(MMS),和更敏感的tk位点x射线的诱变效应,EMS, MMS和丝裂霉素c tk突变体的分子分析Southern-hybridization表明70%的自发突变和86%的x射线诱导突变TK6细胞造成损失整个tk基因(杂合性的损失;而WTK-1细胞95%的自发突变和100%的x射线诱导突变显示LOH。密度分析显示，WTK-1细胞中几乎所有的LOH突变体在tk位点上都是纯合的，这与等位基因间同源重组或基因转换一致。这些数据表明p53突变的WTK-1细胞是超可变的，对某些环境诱变物敏感，并且由于其异常高的重组活性，容易发生loh型基因突变。这可能是p53突变细胞的遗传不稳定性在多步骤致瘤过程中显著促进了LOH突变的后续发生。
To investigate the role of p53 as a guardian of the genome, the mutagenic and cytotoxic responses to mutagens were compared for normal (TK6) and p53-mutated (WTK-1) cells. The characteristics of the mutations that occurred in these cells was also examined. Human lymphoblastoid cell lines TK6 and WTK-1 are derived from the same progenitor cell line, but WTK-1 cells have homozygous p53 mutations resulting in overproduction of mutant p53 protein. The spontaneous mutation frequency at the heterozygous thymidine kinase (tk) locus in TK6 and WTK-1 cells was 3.5 X 10(-6) and 101.1 X 10(-6), respectively. WTK-1 cells were more resistant than TK6 cells to cytotoxic damage by X-rays, ethyl methanesulfonate (EMS) and methyl methanesulfonate (MMS), and were more sensitive at the tk locus to the mutagenic effects of X-rays, EMS, MMS and mitomycin C. Molecular analysis of TK mutants by Southern-hybridization demonstrated that 70% of spontaneous mutations and 86% of X-ray induced mutations in TK6 cells resulted from loss of the entire tk allele (loss of heterozygosity; LOH), while 95% of spontaneous and 100% of X-ray induced mutations showed LOH in WTK-1 cells. Densimetric analysis revealed that almost all of the LOH mutants in WTK-1 cells were homozygous at the tk locus, consistent with inter-allelic homologous recombination, or gene conversion. These data indicate that p53-mutated WTK-1 cells are hypermutable, susceptible to some environmental mutagens, and prone to LOH-type gene mutations because of their abnormally high recombinational activity. It may be that genetic instability in p53-mutated cells significantly contribute to the subsequent occurrence of LOH mutations during a multistep tumorigenic process.