Krokan H, Cooke L, Prydz H
Biochemistry. 1975 Sep 23;14(19):4233-7. doi: 10.1021/bi00690a013.
Optimum conditions for a DNA synthesizing system based on isolated nuclei have been described (Krokan, H., Bjorklid, E., and Prydz, H. (1975), Biochemistry, preceding paper in this issue) [3H]TTP-labeled nascent DNA produced during very short pulses was analyzed by centrifugation in alkaline sucrose gradients. More than 80% of the radioactivity appeared in 2-4S pieces (primary DNA pieces). It would therefore seem that the synthesis of DNA is discontinuous both in the 5' leads to 3' and in the 3' leads to 5' directions. The size of the primary DNA pieces increases from 2-4 S up to 14 S with increasing pulse length. Evidence is presented that this increase is not caused by ligation between 2-4S primary pieces. Pulse-chase experiments showed that in this nuclear system primary pieces were ligated to a product generally larger than 30 S. Evidence is also given for the initiation of primary DNA pieces in vitro.
基于分离细胞核的DNA合成系统的最佳条件已有描述（克罗坎，H.，比约克利德，E.，和普吕茨，H.（1975年），《生物化学》，本期前一篇论文）。通过在碱性蔗糖梯度中离心分析了极短脉冲期间产生的[³H]TTP标记的新生DNA。超过80%的放射性出现在2-4S片段（初级DNA片段）中。因此，似乎DNA的合成在5'至3'方向和3'至5'方向都是不连续的。随着脉冲长度的增加，初级DNA片段的大小从2-4S增加到14S。有证据表明，这种增加不是由2-4S初级片段之间的连接引起的。脉冲追踪实验表明，在这个核系统中，初级片段被连接到通常大于30S的产物上。也有证据表明在体外初级DNA片段的起始。
