Bypass of a Nick by the Replisome of Bacteriophage T7
Bypass of a Nick by the Replisome of Bacteriophage T7
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DOI：
10.1074/jbc.m111.252023
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发表时间：
2011-08-12
影响因子：
4.8
通讯作者：
Richardson, Charles C.
中科院分区：
文献类型：
--
作者：
Zhu, Bin;Lee, Seung-Joo;Richardson, Charles C.
DNA聚合酶和DNA解旋酶是DNA复制的重要组成部分。解旋酶解开双链DNA，为DNA聚合酶合成DNA提供单链模板。在噬菌体T7中，DNA解旋酶或DNA聚合酶的运动在遇到双链DNA中的缺口时终止。利用一个小环状DNA，我们证明了解旋酶。聚合酶复合物可以绕过非模板链上的缺口，继续滚动环状DNA合成，尽管效率降低了7%。非模板链上的间隙不能被绕过。旁路合成的效率取决于缺口下游的DNA序列。模板链上的缺口不能被绕过。将T7单链dna结合蛋白添加到复合物中可刺激缺口旁路2倍。我们提出，解旋酶与聚合酶的结合可以防止在遇到缺口时解旋酶的解离，从而使解旋酶在缺口下游继续解绕双链。
DNA polymerase and DNA helicase are essential components of DNA replication. The helicase unwinds duplex DNA to provide single-stranded templates for DNA synthesis by the DNA polymerase. In bacteriophage T7, movement of either the DNA helicase or the DNA polymerase alone terminates upon encountering a nick in duplex DNA. Using a minicircular DNA, we show that the helicase.polymerase complex can bypass a nick, albeit at reduced efficiency of 7%, on the non-template strand to continue rolling circle DNA synthesis. A gap in the non-template strand cannot be bypassed. The efficiency of bypass synthesis depends on the DNA sequence downstream of the nick. A nick on the template strand cannot be bypassed. Addition of T7 single-stranded DNA-binding protein to the complex stimulates nick bypass 2-fold. We propose that the association of helicase with the polymerase prevents dissociation of the helicase upon encountering a nick, allowing the helicase to continue unwinding of the duplex downstream of the nick.