Schuetz J D, Diasio R B
Biochem Biophys Res Commun. 1985 Nov 27;133(1):361-7. doi: 10.1016/0006-291x(85)91884-4.
The effect of 5-fluorouracil (FUra) on DNA elongation was assessed in intact bone marrow cells that had been pulsed for 1 hr with [3H]-dThd in the absence or presence of FUra, chased in fresh media from 0 to 3 hr, and then analyzed on alkaline sucrose gradients. While DNA from control cells elongated at an average rate of 86 nucleotides per sec over a 3 hr interval, DNA from FUra-treated cells did not elongate and in contrast decreased in size over the same interval. In a parallel study to examine what happens to the FUra that was incorporated into DNA, bone marrow cells were pulsed for 1 hr with 50 microM [3H]-FUra, and then chased in fresh media from 0 to 2 hr. An aliquot of cells from each time point was lysed on an alkaline sucrose gradient to assess the size of [3H]-FUra-containing DNA, while another aliquot of cells from each time point was analyzed for radioactivity remaining in total DNA. The percentage of replicon-size DNA (greater than or equal to 100S) containing radiolabel decreased over the 2 hr chase while the percentage of small molecular weight DNA (greater than or equal to 7.2S) increased over the same interval. These changes in DNA size were accompanied by a decrease in radioactivity in total DNA. These studies suggest that excision of FUra from nascent DNA chains may prevent further elongation of DNA.
在完整的骨髓细胞中评估了5-氟尿嘧啶（FUra）对DNA延伸的影响。这些细胞在不存在或存在FUra的情况下用[³H]-dThd脉冲处理1小时，然后在新鲜培养基中从0小时到3小时进行追踪，随后在碱性蔗糖梯度上进行分析。在3小时的时间段内，对照细胞的DNA平均以每秒86个核苷酸的速率延伸，而经FUra处理的细胞的DNA没有延伸，相反，在相同时间段内其大小减小。在一项平行研究中，为了研究掺入DNA中的FUra会发生什么情况，骨髓细胞用50微摩尔的[³H]-FUra脉冲处理1小时，然后在新鲜培养基中从0小时到2小时进行追踪。从每个时间点取出的一份细胞在碱性蔗糖梯度上裂解，以评估含[³H]-FUra的DNA的大小，而从每个时间点取出的另一份细胞则分析总DNA中剩余的放射性。在2小时的追踪过程中，含放射性标记的复制子大小的DNA（大于或等于100S）的百分比下降，而小分子质量DNA（大于或等于7.2S）的百分比在相同时间段内增加。DNA大小的这些变化伴随着总DNA中放射性的降低。这些研究表明，从新生DNA链中切除FUra可能会阻止DNA的进一步延伸。
