Yagi T, Tatsumi-Miyajima J, Sato M, Kraemer K H, Takebe H
Department of Experimental Radiology, Faculty of Medicine, Kyoto University, Japan.
Cancer Res. 1991 Jun 15;51(12):3177-82.
To assess the contribution to mutagenesis by human DNA repair defects, a UV-treated shuttle vector plasmid, pZ189, was passed through fibroblasts derived from Japanese xeroderma pigmentosum (XP) patients in two different DNA repair complementation groups (A and F). Patients with XP have clinical and cellular UV hypersensitivity, increased frequency of skin cancer, and defects in DNA repair. The XP DNA repair defects represented by complementation groups A (XP-A) and F (XP-F) are more common in Japan than in Europe or the United States. In comparison to results with DNA repair-proficient human cells (W138-VA13), UV-treated pZ189 passed through the XP-A [XP2OS(SV)] or XP-F [XP2YO(SV)] cells showed fewer surviving plasmids (XP-A less than XP-F) and a higher frequency of mutated plasmids (XP-A greater than XP-F). Base sequence analysis of more than 200 mutated plasmids showed the major type of base substitution mutation to be the G:C----A:T transition with all three cell lines. The XP-A and XP-F cells revealed a higher frequency of G:C----A:T transitions and a lower frequency of transversions among plasmids with single or tandem mutations and a lower frequency of plasmids with multiple point mutations compared to the normal line. The spectrum of mutations in pZ189 with the XP-A cells was similar to that with the XP-F cells. Seventy-six to 91% of the single base substitution mutations occurred at G:C base pairs in which the 5'-neighboring base of the cytosine was thymine or cytosine. These studies indicate that the DNA repair defects in Japanese XP patients in complementation groups A and F result in different frequencies of plasmid survival and mutagenesis but in similar types of mutagenic abnormalities despite marked differences in clinical features. These results, together with comparable studies from United States patients in XP complementation groups A and D, suggest that G:C----A:T somatic mutations may be important in the generation of human skin cancer by UV radiation.
为评估人类DNA修复缺陷对诱变的影响，将经紫外线处理的穿梭载体质粒pZ189，通过来自日本着色性干皮病（XP）患者的成纤维细胞，这些患者分属于两个不同的DNA修复互补组（A组和F组）。XP患者具有临床和细胞水平的紫外线超敏反应、皮肤癌发生率增加以及DNA修复缺陷。互补组A（XP-A）和F（XP-F）所代表的XP DNA修复缺陷在日本比在欧洲或美国更为常见。与DNA修复功能正常的人类细胞（W138-VA13）的结果相比，经紫外线处理的pZ189通过XP-A [XP2OS(SV)] 或XP-F [XP2YO(SV)] 细胞后，存活的质粒较少（XP-A组少于XP-F组），而突变质粒的频率较高（XP-A组大于XP-F组）。对200多个突变质粒的碱基序列分析表明，所有三种细胞系中碱基替换突变主要类型都是G:C→A:T转换。与正常细胞系相比，XP-A和XP-F细胞在单突变或串联突变的质粒中显示出较高的G:C→A:T转换频率和较低的颠换频率，以及具有多个点突变的质粒频率较低。pZ189在XP-A细胞中的突变谱与在XP-F细胞中的相似。76%至91%的单碱基替换突变发生在G:C碱基对，其中胞嘧啶的5'相邻碱基为胸腺嘧啶或胞嘧啶。这些研究表明，日本XP患者互补组A和F中的DNA修复缺陷导致质粒存活和诱变频率不同，但诱变异常类型相似，尽管临床特征存在显著差异。这些结果，连同来自美国XP互补组A和D患者的类似研究，表明G:C→A:T体细胞突变可能在紫外线辐射诱发人类皮肤癌过程中起重要作用。
