Removal of O6-methylguanine from DNA of normal and xeroderma pigmentosum-derived lymphoblastoid lines
Removal of O6-methylguanine from DNA of normal and xeroderma pigmentosum-derived lymphoblastoid lines
复制标题
从正常和着色性干皮病衍生的淋巴母细胞系 DNA 中去除 O6-甲基鸟嘌呤
作者：
R. Sklar;B. Strauss
在大肠杆菌中，切除（修复）UV诱导的嘧啶二聚体的能力与其从DNA 1中去除N-甲基-N′-硝基-N-亚硝基胍（MNNG）诱导的O 6-甲基-鸟嘌呤（O 6-MeG）的能力无关。因此，令人惊讶的是，某些缺乏二聚体切除的着色性干皮病细胞系也不能去除O 6-MeG 1 -3。我们发现，O 6-MeG的去除发生迅速，半衰期小于1小时。可以区分两种细胞类型：mex+，它去除与0.5 µg ml−1 MNNG孵育产生的O 6-MeG残留物，和mex−细胞，它不能去除加合物。着色性干皮病衍生的互补群A、C或D的类淋巴母细胞系可以是mex+或mex-。在人体细胞中去除O 6-MeG的生化机制不同于切除由化合物如N-乙酰氧基-N-2-乙酰氨基芴（AAAF）或紫外线照射产生的加合物，但目前尚不清楚mex+和mex−系之间的区别是遗传还是表观遗传。
The ability to excise (repair) UV-induced pyrimidine dimers in Escherichia coli is not related to its ability to remove N-methyl-N′-nitro-N-nitrosoguanidine (MNNG)-induced O6-methyl-guanine (O6-MeG) from DNA1. It was therefore surprising that certain xeroderma pigmentosum cell lines, deficient in dimer excision, were also unable to remove O6-MeG1–3 We find that removal of O6-MeG occurs rapidly with a half life of less than 1 h. Two cell types can be distinguished: mex+, which remove O6-MeG residues produced by incubation with 0.5 µg ml−1 MNNG, and mex− cells, which are unable to remove the adduct. Xeroderma pigmentosum-derived lymphoblastoid lines of complementation groups A, C or D may be either mex+ or mex−. The biochemical mechanism for the removal of O6-MeG in human cells is distinct from the excision of adducts produced by compounds such as N-acetoxy-N-2-acetylaminofluorene (AAAF) or by UV irradiation but it is not clear whether the distinction between mex+ and mex− lines is genetic or epigenetic.