Schuetz J D, Collins J M, Wallace H J, Diasio R B
Cancer Res. 1986 Jan;46(1):119-23.
The present study evaluates the effects of 5-fluorouracil (FUra) on the structure of newly synthesized DNA purified from bone marrow cells. DNA synthesis was decreased by 30 and 45% of control in the presence of 19 and 100 microM FUra, respectively. Furthermore at these concentrations of FUra, the DNA strand sizes were smaller as determined by alkaline sucrose gradients. Enzymatic digestion of the DNA demonstrated that most of the FUra (greater than 90%) was localized in the internucleotide linkage and not at the chain terminus. As the concentration of FUra was varied, the percentage of FUra at the chain terminus was unchanged, suggesting that the decrease in chain size as well as inhibition of DNA synthesis was not due to chain termination. DNA that had been synthesized in the presence of FUra was shown to fragment after increasing time as demonstrated by alkaline sucrose gradient analysis. This time-dependent fragmentation was associated with an increased number of strand breaks as determined by neutral and alkaline sucrose gradient analysis. A parallel study demonstrated a time-dependent excision of FUra from DNA over this same time period. In summary, these studies demonstrate an association between the excision of FUra from DNA and the changes in secondary structure of newly synthesized DNA.
本研究评估了5-氟尿嘧啶（FUra）对从骨髓细胞中纯化的新合成DNA结构的影响。在存在19 microM和100 microM FUra的情况下，DNA合成分别降低至对照的30%和45%。此外，在这些FUra浓度下，通过碱性蔗糖梯度测定，DNA链的大小较小。DNA的酶切表明，大部分FUra（大于90%）位于核苷酸间连接处，而非链末端。随着FUra浓度的变化，链末端的FUra百分比不变，这表明链大小的减小以及DNA合成的抑制并非由于链终止。如碱性蔗糖梯度分析所示，在FUra存在下合成的DNA在延长时间后会发生片段化。通过中性和碱性蔗糖梯度分析确定，这种时间依赖性片段化与链断裂数量的增加有关。一项平行研究表明，在同一时间段内，FUra会从DNA中发生时间依赖性切除。总之，这些研究证明了FUra从DNA中切除与新合成DNA二级结构变化之间的关联。
