Strathern J N, Shafer B K, McGill C B
Laboratory of Eukaryotic Gene Expression, NCI-Frederick Cancer Research and Development Center, ABL-Basic Research Program, Maryland 21702-1201, USA.
Genetics. 1995 Jul;140(3):965-72. doi: 10.1093/genetics/140.3.965.
Repair of a site-specific double-strand DNA break (DSB) resulted in increased reversion frequency for a nearby allele. Site-specific DSBs were introduced into the genome of Saccharomyces cerevisiae by the endonuclease encoded by the HO gene. Expression of the HO gene from a galactose-inducible promoter allowed efficient DNA cleavage at a single site in large populations of cells. To determine whether the DNA synthesis associated with repair of DSBs has a higher error rate than that associated with genome duplication, HO-induced DSBs were generated 0.3 kb from revertible alleles of trp1. The reversion rate of the trp1 alleles was approximately 100-fold higher among cells that had experienced an HO cut than among uninduced cells. The reverted allele was found predominantly on the chromosome that experienced the DNA cleavage.
位点特异性双链DNA断裂（DSB）的修复导致附近等位基因的回复频率增加。通过HO基因编码的核酸内切酶将位点特异性DSB引入酿酒酵母基因组。来自半乳糖诱导型启动子的HO基因表达允许在大量细胞的单个位点进行高效的DNA切割。为了确定与DSB修复相关的DNA合成是否比与基因组复制相关的DNA合成具有更高的错误率，在距trp1的可回复等位基因0.3 kb处产生HO诱导的DSB。在经历过HO切割的细胞中，trp1等位基因的回复率比未诱导细胞中的回复率高约100倍。回复的等位基因主要出现在经历DNA切割的染色体上。
