Tsubota Y, Waqar M A, Davis L R, Spotila L, Huberman J A
Biochemistry. 1982 May 25;21(11):2713-8. doi: 10.1021/bi00540a021.
We have measured the relative accessibility to a single-strand-specific endonuclease of the single-stranded DNA on the leading and lagging sides of replication forks in replicating simian virus 40 (SV40) chromosomes. To do this we have digested replicating SV40 chromosomes with a single-strand-specific endonuclease (P1 nuclease) and then characterized the intermediate and final products of digestion by sucrose gradient sedimentation and agarose gel electrophoresis. P1 nuclease rapidly and specifically cleaves parental DNA strands at replication forks, yielding intermediate and final cleavage products which are consistent with an approximately equal rate of nuclease cleavage on both sides of the fork. Thus, single-stranded DNA is approximately as accessible to P1 nuclease on the leading side of the fork as on the lagging side; the simplest interpretation of this observation is that the stretch of single-stranded DNA on the leading side is as long as that on the lagging side.
我们已经测量了在复制猴病毒40（SV40）染色体时，复制叉前导链和后随链上的单链DNA对单链特异性核酸内切酶的相对可及性。为此，我们用单链特异性核酸内切酶（P1核酸酶）消化正在复制的SV40染色体，然后通过蔗糖梯度沉降和琼脂糖凝胶电泳对消化的中间产物和最终产物进行表征。P1核酸酶在复制叉处快速且特异性地切割亲本DNA链，产生的中间切割产物和最终切割产物与核酸酶在复制叉两侧以大致相等的速率切割相一致。因此，复制叉前导链上的单链DNA对P1核酸酶的可及性与后随链上的大致相同；对这一观察结果最简单的解释是，前导链上的单链DNA片段与后随链上的一样长。
