Holmberg M
National Institute of Radiation Protection, Stockholm, Sweden.
Mutat Res. 1989 Jul;218(1):33-9. doi: 10.1016/0921-8777(89)90044-x.
UVC irradiation of mammalian cells induces DNA lesions, which can give rise to transient DNA breaks at subsequent incubation of the cells. The yield of these transient DNA breaks depends on the incision rate as well as on the polymerase and ligation rates. It has previously been shown that the yield of transient DNA breaks is drastically lowered in human lymphocytes if the 4 deoxynucleosides are added to the culture medium during the repair period after UVC irradiation. The present results show that addition of the combination dAdo dGuo dThd or addition of the combination dAdo dThd also efficiently reduces the yield of transient DNA breaks during a repair period of 3 h after the UVC irradiation. Other combinations of deoxynucleosides are less efficient or not efficient at all. This indicates that the pool sizes of dATP and dTTP affect the yield of transient DNA breaks in human lymphocytes. However, the present data also indicate that the number of processed repair sites does not increase during the repair period after UVC irradiation, if the combination dAdo dThd is present in the culture medium during the repair period. Therefore, it is proposed that the presence of dAdo dThd affects the rate of insertion of repair patches but not the total amount of synthesized and inserted patches.
哺乳动物细胞经紫外线C（UVC）照射会诱导DNA损伤，在随后的细胞培养过程中，这种损伤可能导致短暂的DNA断裂。这些短暂DNA断裂的产生率取决于切割速率以及聚合酶和连接速率。此前有研究表明，如果在UVC照射后的修复期向培养基中添加4种脱氧核苷，人类淋巴细胞中短暂DNA断裂的产生率会大幅降低。目前的研究结果表明，添加腺嘌呤脱氧核苷（dAdo）、鸟嘌呤脱氧核苷（dGuo）、胸腺嘧啶脱氧核苷（dThd）的组合，或者添加腺嘌呤脱氧核苷（dAdo）和胸腺嘧啶脱氧核苷（dThd）的组合，在UVC照射后的3小时修复期内也能有效降低短暂DNA断裂的产生率。其他脱氧核苷组合的效果较差或根本无效。这表明三磷酸腺苷（dATP）和三磷酸胸苷（dTTP）的库大小会影响人类淋巴细胞中短暂DNA断裂的产生率。然而，目前的数据还表明，如果在修复期培养基中存在腺嘌呤脱氧核苷（dAdo）和胸腺嘧啶脱氧核苷（dThd）的组合，在UVC照射后的修复期内处理的修复位点数量不会增加。因此，有人提出，腺嘌呤脱氧核苷（dAdo）和胸腺嘧啶脱氧核苷（dThd）的存在会影响修复片段的插入速率，但不会影响合成和插入片段的总量。
