EXPRESSION OF A TRANSFECTED DNA-REPAIR GENE (XPA) IN XERODERMA-PIGMENTOSUM GROUP-A CELLS RESTORES NORMAL DNA-REPAIR AND MUTAGENESIS OF UV-TREATED PLASMIDS
EXPRESSION OF A TRANSFECTED DNA-REPAIR GENE (XPA) IN XERODERMA-PIGMENTOSUM GROUP-A CELLS RESTORES NORMAL DNA-REPAIR AND MUTAGENESIS OF UV-TREATED PLASMIDS
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DOI：
10.1093/carcin/16.7.1557
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发表时间：
1995-07-01
期刊：
影响因子：
4.7
通讯作者：
KRAEMER, KH
中科院分区：
文献类型：
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作者：
LEVY, DD;SAIJO, M;KRAEMER, KH
XPA 基因最初是基于其 cDNA 在紫外线照射后提高着色性干皮病互补组 A (XP-A) 患者细胞存活率的能力进行克隆的。我们使用质粒宿主细胞再激活测定来比较 XP-A 患者细胞系 XP2OS(SV40)、稳定表达 XPA cDNA 的两种衍生细胞系和 DNA 修复熟练的人类细胞系中的 UV 诱变和 DNA 修复能力，表达XP2OS细胞中XPA蛋白的表达使它们能够修复经紫外线处理的质粒pRSVCAT，将受损CAT标记基因的活性提高到正常细胞中类似受损质粒产生的水平>100倍。XP2OS细胞中XPA蛋白的表达改善了经紫外线处理的穿梭载体pSP189的复制，增加了质粒存活并将质粒突变频率降低至正常细胞中测量的水平。三种细胞系的质粒标记基因中大多数突变热点的序列位置相似，并且差异与细胞的DNA修复状态无关，这表明突变热点的位置不受DNA修复的直接影响，XPA蛋白的表达确实引起了质粒基因中观察到的突变类型的转变，在XP2OS细胞中> 95％的质粒突变是G：C-->A：T过渡突变，相反，表达XPA的XP2OS细胞产生其他类型的突变：颠换突变数量是原来的三倍，A:T碱基对突变增加了12倍，此外，这些类型突变的分布与正常细胞中测量的比例相似，通过检查含有p53肿瘤抑制基因突变的XP和非XP皮肤癌的报告，发现了惊人相似的转换和颠换突变模式，表明细胞的修复状态影响了与这些皮肤癌相关的突变，我们的数据表明XPA基因功能的丧失可能足以影响与 XP-A 患者皮肤癌大量增加相关的诱变的量和质的变化。
The XPA gene was initially cloned based on the ability of its cDNA to improve survival of cells from xeroderma pigmentosum complementation group A (XP-A) patients following irradiation of the cells with UV, We used plasmid host cell reactivation assays to compare UV mutagenesis and the proficiency of DNA repair in a cell line from an XP-A patient, XP2OS(SV40), two derivative cell lines stably expressing XPA cDNAs and in a DNA repair proficient human cell line, Expression of XPA protein in XP2OS cells allowed them to repair UV-treated plasmid pRSVCAT, increasing activity of the damaged CAT marker gene >100-fold to levels produced by similarly damaged plasmids in normal cells, Expression of the XPA protein in XP2OS cells improved replication of the UV-treated shuttle vector pSP189, increasing plasmid survival and decreasing plasmid mutation frequency to the levels measured in normal cells. The sequence locations of most mutation hotspots in the plasmid marker gene were similar for the three cell lines and the differences did not correlate with the DNA repair status of the cells, This suggests that the location of mutation hotspots is not directly influenced by DNA repair, Expression of the XPA protein did cause a shift in the types of mutations seen in the plasmid gene, In the XP2OS cells >95% of the plasmid mutations were G:C-->A:T transition mutations, In contrast, XP2OS cells expressing XPA produced other types of mutations: three times as many transversion mutations and a 12-fold increase in mutations at A:T base pairs, Furthermore, the distribution of these types of mutations was similar to the proportions measured in normal cells, Strikingly similar patterns of transition and transversion mutations were found by examination of reports of XP and non-XP skin carcinomas containing mutations in the p53 tumor supressor gene, suggesting that the repair status of the cells influenced mutagenesis associated with these skin cancers, Our data suggest that loss of XPA gene function may be sufficient to effect the quantitative and qualitative changes in mutagenesis associated with the large increase in skin cancers seen in XP-A patients.