Analysis of mutations induced in cells derived from DNA repair-deficient hereditary disease patients.

为了评价DNA修复缺陷对DNA修复缺陷致突变的作用，将诱变剂处理的穿梭载体载体通过3个不同的DNA修复互补组(A、C和F)、远程共济失调(AT)患者和小鼠的色素性干皮病(XP)患者的成纤维细胞。与熟悉DNA修复的正常人类细胞相比，紫外线处理的穿梭载体载体通过XP-A、C或F细胞的存活质粒较少(XP-A小于C和F)，而突变质粒(XP-A大于C和F)的频率更高。在碱基替换突变中，3种细胞系的替换类型均以G：C-&GT；A：T转换为主。与正常对照相比，XP-A、C和F细胞的G：C-&A：T转换频率较高，横纹频率较低。XP-A细胞的突变谱与XP-C和F细胞相似。大多数单碱基替换突变发生在G：C碱基对上，其中胞嘧啶的5‘端碱基为嘧啶。在自发突变体中，超过50%的突变体存在缺失，其余的突变体存在碱基替换，颠换频率很高。在紫外线诱导的小鼠细胞碱基替换突变体中，91%的突变体存在G：C-&GT；A：T转变。γ射线照射后的AT细胞和正常细胞在存活率和突变率方面无明显差异。内切酶限制的载体DNA重连接效率在AT细胞和正常细胞中相似，但在正常细胞中重连接的保真度高于AT细胞。在O^6-烷基鸟嘌呤修复缺陷小鼠细胞中，甲基亚硝脲诱发突变的频率特别是G：C-&GT；A：T转变的频率高于熟练的小鼠细胞。

To assess the contribution to mutagenesis by DAN repair defects, mutagen-treated shuttle vector plasmids were passed through fibroblasts derived from xeroderma pigmentosum(XP)patients in 3 different DNA repair complementation groups(A, C and F), ataxia telangectasia(AT)patients and mice.In comparison to DNA repair proficient normal human cells, the UV-treated plasmed passed through the XP-A, C or F cells showed fewer surviving plasmids(XP-A less than C and F)and a higher frequency of mutated plasmids(XP-A greater than C and F). Among base substitution mutations, the major type of the substitution was G : C -> A : T transition in all 3 cell lines. The XP-A, C and F cells revealed a hlgher frequency of G : C -> A : T transition along with a lower frequency of transverslons compared to the normal line. The spectrum of mutations In the XP-A cells was similar to that in the XP-C and F cells. Most single base substitution mutations occurred at G : C base pairs in which the 5'-nelghboring base of the cytosine was a pyrimidine. In spontaneous mutants, more than 50% mutants have a deletion, and the rest have base substitutions with a high frequency of transversions. Among UV-Induced base substitution mutants from mouse cells, 91% mutants have G : C -> A : T transition. gamma -ray-irradiated plasmids passed through AT and normal cells showed no significant difference in the survival and a frequency of mutated plasmed. Efficiency of rejoining of vector DNA restricted by an endonuclease was similar between AT and normal cells, but fidelity of the rejoining is higher in the normal than AT cells. A frequency of methyl nitrosourea-induced mutations, especially G : C -> A : T transition was higher in O^6-alkylguanine-repair deficient mouse cells than the proficient mouse cells.In this study, a role of DNA repair for the Induction of mutation in molecular level was clarified by using shuttle vectors and DNA repair deficient cells.