Campbell C R, Ayares D, Watkins K, Wolski R, Kucherlapati R
Department of Genetics, University of Illinois College of Medicine, Chicago 60612.
Mutat Res. 1989 Mar;211(1):181-8. doi: 10.1016/0027-5107(89)90118-8.
Uniformly methylated heteroduplex plasmids which contained 6 mismatched regions, including loops of 24, 30, 248 and 283 nucleotides, as well as single-stranded gaps and free ends were introduced into a recombination-deficient strain of bacteria, and the products of repair were analyzed. The results indicate that these cells are capable of repairing all of these structures, although with different efficiencies. Repair of single-stranded gaps and free ends, which occurs most efficiently, is always associated with acquisition of information from the uncut strand (unidirectional repair). Regions containing single loops or twin loops were repaired at similar efficiencies. In these cases each of the two strands was capable of acting as the template for repair (bidirectional repair). At sites containing twin or substitution loops, the larger of the loops was removed twice as efficiently as the smaller loop. DNA sequencing of the repaired regions indicated that the repair is precise. The data also suggest that markers separated by only 58 nucleotides do not always segregate together indicating that repair tracts may be relatively short.
将含有6个错配区域的均匀甲基化异源双链质粒导入重组缺陷型细菌菌株中，这些错配区域包括24、30、248和283个核苷酸的环，以及单链缺口和游离末端，然后分析修复产物。结果表明，这些细胞能够修复所有这些结构，尽管效率不同。单链缺口和游离末端的修复效率最高，且总是与从未切割链获取信息相关联（单向修复）。含有单环或双环的区域以相似的效率进行修复。在这些情况下，两条链中的每一条都能够作为修复模板（双向修复）。在含有双环或替代环的位点，较大的环被去除的效率是较小环的两倍。对修复区域的DNA测序表明修复是精确的。数据还表明，仅相隔58个核苷酸的标记并不总是一起分离，这表明修复片段可能相对较短。
