Boyle J M, Schenley R L, Swenson P A
J Bacteriol. 1971 Jun;106(3):896-903. doi: 10.1128/jb.106.3.896-903.1971.
Ultraviolet irradiation (520 ergs/mm(2) at 254 nm) causes the respiration of Escherichia coli B/r cells to cease after about 90 min postirradiation incubation in a minimal medium containing glycerol as the sole source of carbon. The cessation of respiration is associated with loss of pyridine nucleotides. Agents which interfere with postirradiation transcription and translation prevent cessation of respiration. We have studied the effects of one of these agents, 5-fluorouracil (FU), on respiration, pyridine nucleotide levels, viability, capacity to support phage growth, and the repair of irradiated deoxyribonucleic acid (DNA). Addition of FU to cells immediately after irradiation results in the continuance of respiration at a linear rate and the maintenance of high levels of pyridine nucleotides. Cellular viability increases dramatically during the first 60 min of postirradiation incubation in the presence of FU. The ability of irradiated cells to support the growth of phage T4 is also greatly increased. FU treatment has no effect on the kinetics of pyrimidine dimer excision or the degradation of DNA. However, treated cells repair single-strand breaks resulting from early steps in excision repair slightly more efficiently than do untreated cells. The results support the hypothesis that one of the causes of death in these irradiated cells is the disappearance of pyridine nucleotides, coenzymes of certain respiratory dehydrogenases, and, in the case of nicotinamide adenine dinucleotide, for polynucleotide ligase, the enzyme responsible for the final step in the repair of DNA.
紫外线照射（254纳米波长下520尔格/平方毫米）会使大肠杆菌B/r细胞在以甘油作为唯一碳源的基本培养基中进行约90分钟的照射后培养后呼吸停止。呼吸停止与吡啶核苷酸的丧失有关。干扰照射后转录和翻译的试剂可防止呼吸停止。我们研究了其中一种试剂5-氟尿嘧啶（FU）对呼吸、吡啶核苷酸水平、活力、支持噬菌体生长的能力以及辐照脱氧核糖核酸（DNA）修复的影响。照射后立即向细胞中添加FU会导致呼吸以线性速率持续，并维持高水平的吡啶核苷酸。在存在FU的情况下，照射后培养的前60分钟内细胞活力显著增加。受照射细胞支持噬菌体T4生长的能力也大大提高。FU处理对嘧啶二聚体切除动力学或DNA降解没有影响。然而，处理后的细胞修复切除修复早期步骤产生的单链断裂的效率略高于未处理的细胞。这些结果支持了这样一种假设，即这些受照射细胞死亡的原因之一是吡啶核苷酸的消失，某些呼吸脱氢酶的辅酶，就烟酰胺腺嘌呤二核苷酸而言，还有负责DNA修复最后一步的多核苷酸连接酶。
