Olivera B M
Proc Natl Acad Sci U S A. 1978 Jan;75(1):238-42. doi: 10.1073/pnas.75.1.238.
We have directly tested the hypothesis that elevated levels of dUTP cause the formation of small DNA fragments at the replication fork of Escherichia coli. Addition of increasing levels of dUTP to lysates on cellophane discs results in an increasing number of strand scissions in the newly replicated DNA. Lysates of strains defective in dUTPase produce many more scissions at the same level of dUTP. The size distribution of Okazaki pieces obtained in vivo can be reconstituted in vitro on cellophane discs if appropriate levels of dUTP are present. Although uracil excision leads to the apparent production of Okazaki pieces from both daughter strands, DNA synthesis is actually asymmetric under these conditions. De novo chain initiation events occur on only one strand. It is suggested that asymmetry of synthesis in vivo may be masked by uracil excision and other postreplication processing mechanisms.
脱氧尿苷三磷酸（dUTP）水平升高会导致大肠杆菌复制叉处形成小的DNA片段。在玻璃纸圆盘上的裂解物中添加不断增加水平的dUTP，会导致新复制的DNA中链断裂的数量增加。dUTPase缺陷型菌株的裂解物在相同dUTP水平下会产生更多的链断裂。如果存在适当水平的dUTP，体内获得的冈崎片段的大小分布可以在玻璃纸圆盘上进行体外重构。尽管尿嘧啶切除会导致两条子链上明显产生冈崎片段，但在这些条件下DNA合成实际上是不对称的。从头链起始事件仅发生在一条链上。有人提出，体内合成的不对称性可能被尿嘧啶切除和其他复制后加工机制所掩盖。
