Snyder R D, Sunkara P S
Merrell Dow Research Institute, Cincinnati, OH 45215.
Photochem Photobiol. 1990 Sep;52(3):525-32. doi: 10.1111/j.1751-1097.1990.tb01795.x.
Treatment of HeLa cells with the polyamine biosynthesis inhibitors, methylglyoxal bis(guanylhydrazone) (MGBG), difluoromethylornithine (DFMO) or a combination of the two, resulted in reduction in cellular polyamine levels. Analysis of UV light-induced DNA damage and repair in these polyamine depleted cells revealed distinct differences in the repair process relative to that seen in cells possessing a normal polyamine complement. Initial yield of thymine dimers and rate of removal of these lesions from cellular DNA appeared normal in polyamine-depleted cells. However, depleted cells exhibited retarded sealing of DNA strand breaks resulting from cellular repair processes, reduced repair synthesis and an increased sensitivity to UV killing. Incision at damaged sites was not affected since ara-C repair-dependent breaks accumulated in a normal fashion. Molecular analysis of inhibited repair sites by exonuclease III and T4 DNA ligase probes suggest that the strand interruptions consist of gaps rather than ligatable nicks, consistent with an interpretation of the repair defect being at the gap-filling stage rather than the ligation step. Observed patterns of differential polyamine depletion by DFMO and MGBG, and partial reversal of repair inhibition by polyamine supplementation, suggests that polyamine depletion per se, rather than some secondary effect of inhibitor treatment, is responsible for the inhibition of repair.
用多胺生物合成抑制剂甲基乙二醛双（脒腙）（MGBG）、二氟甲基鸟氨酸（DFMO）或两者联合处理HeLa细胞，导致细胞内多胺水平降低。对这些多胺耗竭细胞中紫外线诱导的DNA损伤和修复进行分析，发现与具有正常多胺含量的细胞相比，修复过程存在明显差异。在多胺耗竭细胞中，胸腺嘧啶二聚体的初始产量和这些损伤从细胞DNA中去除的速率看起来正常。然而，耗竭细胞表现出细胞修复过程导致的DNA链断裂的封闭延迟、修复合成减少以及对紫外线杀伤的敏感性增加。由于阿糖胞苷修复依赖性断裂以正常方式积累，受损位点的切割不受影响。用核酸外切酶III和T4 DNA连接酶探针抑制修复位点的分子分析表明，链中断由缺口而非可连接的切口组成，这与修复缺陷在于缺口填充阶段而非连接步骤的解释一致。观察到的DFMO和MGBG对多胺耗竭的差异模式，以及多胺补充对修复抑制的部分逆转，表明多胺耗竭本身而非抑制剂处理的某些次要效应是修复抑制的原因。
