Youngs D A, Smith K C
J Bacteriol. 1973 Apr;114(1):121-7. doi: 10.1128/jb.114.1.121-127.1973.
A polA1 exrA strain of Escherichia coli K-12 was constructed. It was found to be more sensitive to aerobic or anoxic X irradiation than were mutants containing either polA1 or exrA alone. The ability of polA1 exrA and related strains to repair X-ray-induced single-strand breaks in deoxyribonucleic acid DNA was examined. The polA1 strain was deficient in type II (buffer) repair but not in type III (growth medium-dependent) repair. The exrA strain was not deficient in type II repair but was deficient in type III repair (similar to rec strains). The double mutant polA1 exrA was deficient in both type II and type III repair. Thus, the increased X-ray sensitivity of the polA1 exrA double mutant was correlated with its decreased ability to repair X-ray-induced single-strand breaks in DNA. We have tested the hypothesis that polA rec double mutants are not viable because they lack the types II and III systems for the repair of DNA single-strand breaks. Since the polA1 exrA strain is viable and is deficient in both of these repair processes, this hypothesis seems not to be correct.
构建了大肠杆菌K-12的polA1 exrA菌株。发现它比单独含有polA1或exrA的突变体对有氧或无氧X射线照射更敏感。检测了polA1 exrA及相关菌株修复X射线诱导的脱氧核糖核酸（DNA）单链断裂的能力。polA1菌株在II型（缓冲液）修复方面存在缺陷，但在III型（生长培养基依赖性）修复方面没有缺陷。exrA菌株在II型修复方面没有缺陷，但在III型修复方面存在缺陷（类似于rec菌株）。双突变体polA1 exrA在II型和III型修复方面均存在缺陷。因此，polA1 exrA双突变体对X射线敏感性的增加与其修复DNA中X射线诱导的单链断裂能力的降低相关。我们已经检验了polA rec双突变体不可行是因为它们缺乏修复DNA单链断裂的II型和III型系统这一假设。由于polA1 exrA菌株是可行的，并且在这两种修复过程中均存在缺陷，所以这个假设似乎不正确。
