Weiss U, Wilson J H
Proc Natl Acad Sci U S A. 1987 Mar;84(6):1619-23. doi: 10.1073/pnas.84.6.1619.
Repair of heteroduplex DNA, generated between two interacting DNA molecules during homologous recombination, has been implicated as a contributing factor in the process of gene conversion. To assess patterns of heteroduplex repair in mammalian cells, we constructed 13 different heteroduplexes from simian virus 40 wild-type and deletion mutant DNAs. Each heteroduplex contained one or multiple single-stranded loops in the intron of the gene for large tumor antigen, which is not essential during lytic infection. After transfection into cultured monkey cells, cellular repair was evaluated by restriction analysis of the amplified viral progeny from 1123 individual plaques, each representing the clonal expansion of a single repair event. Single-stranded loops were corrected prior to replication with an overall efficiency of 90%. At the position of a loop, one of the two heteroduplex strands served as a template for accurate repair 98% of the time. Repair of single-stranded loops was biased nearly 2 to 1 in favor of the strand without the loop. The efficiency, accuracy, and strand bias of repair were unaffected by loop size within the tested range, which was 25-247 nucleotides. The excision tract associated with repair of single-stranded loops rarely exceeds 200-400 nucleotides in length.
在同源重组过程中，两个相互作用的DNA分子之间产生的异源双链DNA的修复被认为是基因转换过程中的一个促成因素。为了评估哺乳动物细胞中异源双链修复的模式，我们用猿猴病毒40野生型和缺失突变型DNA构建了13种不同的异源双链。每个异源双链在大肿瘤抗原基因的内含子中包含一个或多个单链环，在裂解感染期间这并非必需。转染到培养的猴细胞后，通过对来自1123个单个噬菌斑的扩增病毒后代进行限制性分析来评估细胞修复情况，每个噬菌斑代表单个修复事件的克隆扩增。单链环在复制前被校正，总体效率为90%。在环的位置，两条异源双链链中的一条有98%的时间作为精确修复的模板。单链环的修复偏向于没有环的链，比例接近2比1。在所测试的25至247个核苷酸范围内，修复的效率、准确性和链偏向不受环大小的影响。与单链环修复相关的切除片段长度很少超过200 - 400个核苷酸。
