Begleiter A, Verburg L, Israels L G, Johnston J B
Department of Internal Medicine, University of Manitoba, Winnipeg, Canada.
Cancer Chemother Pharmacol. 1992;30(1):65-9. doi: 10.1007/BF00686487.
Permeabilized L5178Y cells were used to investigate the mechanism underlying inhibition of the repair of irradiation-induced DNA strand breaks by 2'-deoxycoformycin combined with deoxyadenosine. Permeabilized cells repaired DNA strand breaks as effectively as did intact cells, and at deoxyadenosine concentrations that produced similar levels of deoxyadenosine triphosphate (dATP), repair of DNA strand breaks was inhibited by 2'-deoxycoformycin plus deoxyadenosine to a comparable extent in both types of cells. Accompanying the increase in intracellular dATP produced by 2'-deoxycoformycin combined with deoxyadenosine was a fall in levels of deoxythymidine triphosphate (dTTP), deoxyguanosine triphosphate (dGTP), and deoxycytidine triphosphate (dCTP). The addition of dTTP, dGTP, and dCTP reversed the inhibition of DNA repair by 2'-deoxycoformycin plus deoxyadenosine, although the level of dATP was not affected. Reducing the phosphorylation of deoxy-adenosine to dATP by the addition of adenosine prevented the decrease in levels of dTTP, dGTP, and dCTP and the inhibition of DNA repair by 2'-deoxycoformycin and deoxyadenosine. In contrast, increasing the intracellular levels of dATP by the addition of 2'-deoxycoformycin together with dATP, deoxyadenosine diphosphate (dADP), or deoxyadenosine monophosphate (dAMP) had no effect on the levels of the other deoxynucleotide triphosphates and did not inhibit DNA repair. Moreover, DNA repair was not inhibited by the breakdown products of deoxyadenosine, adenine, or deoxyribose. These results suggest that inhibition of the repair of irradiation-induced DNA strand breaks by 2'-deoxycoformycin combined with deoxyadenosine requires the phosphorylation of deoxyadenosine and involves alterations in the levels of deoxynucleotide triphosphates.
使用通透化的L5178Y细胞来研究2'-脱氧助间型霉素联合脱氧腺苷抑制辐射诱导的DNA链断裂修复的潜在机制。通透化细胞修复DNA链断裂的效率与完整细胞相同，并且在产生相似水平三磷酸脱氧腺苷（dATP）的脱氧腺苷浓度下，2'-脱氧助间型霉素加脱氧腺苷对两种类型细胞中DNA链断裂修复的抑制程度相当。随着2'-脱氧助间型霉素联合脱氧腺苷使细胞内dATP增加，三磷酸脱氧胸苷（dTTP）、三磷酸脱氧鸟苷（dGTP）和三磷酸脱氧胞苷（dCTP）水平下降。添加dTTP、dGTP和dCTP可逆转2'-脱氧助间型霉素加脱氧腺苷对DNA修复的抑制作用，尽管dATP水平不受影响。通过添加腺苷减少脱氧腺苷磷酸化为dATP可防止dTTP、dGTP和dCTP水平下降以及2'-脱氧助间型霉素和脱氧腺苷对DNA修复的抑制。相反，通过添加2'-脱氧助间型霉素与dATP、二磷酸脱氧腺苷（dADP）或一磷酸脱氧腺苷（dAMP）一起增加细胞内dATP水平对其他三磷酸脱氧核苷酸水平没有影响，也不抑制DNA修复。此外，脱氧腺苷、腺嘌呤或脱氧核糖的分解产物不会抑制DNA修复。这些结果表明，2'-脱氧助间型霉素联合脱氧腺苷抑制辐射诱导的DNA链断裂修复需要脱氧腺苷磷酸化，并涉及三磷酸脱氧核苷酸水平的改变。
