DNA HELICASE REQUIREMENTS FOR DNA-REPLICATION DURING BACTERIOPHAGE-T4 INFECTION
DNA HELICASE REQUIREMENTS FOR DNA-REPLICATION DURING BACTERIOPHAGE-T4 INFECTION
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DOI：
10.1128/jb.176.6.1667-1672.1994
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发表时间：
1994-03-01
影响因子：
3.2
通讯作者：
HACKER, KJ
中科院分区：
文献类型：
--
作者：
GAUSS, P;PARK, K;HACKER, KJ
裂解噬菌体T4使用多种机制启动其DNA的复制。在感染的早期，起始主要发生在复制起始处，但在感染的后期，有一种向遗传重组依赖的起始的转变。T4插入-替代系统被用来在T4dda基因上产生缺失，该基因编码一个5‘-3’DNA解旋酶，在体外刺激DNA复制和重组反应。该缺失导致T4DNA合成在感染早期延迟，提示DDA蛋白参与了依赖起源的DNA合成的启动。然而，DNA合成最终达到了接近野生型的水平，每个细菌最终产生的噬菌体数量与野生型相似。当dda突变噬菌体还包含T4基因59的突变时(该基因通常只需要依赖重组的DNA复制)，基本上没有合成DNA。最近的体外研究表明，基因59蛋白将原始体的一个组成部分，即T4基因41DNA解旋酶加载到DNA上。基于我们的遗传数据，提出了一个复制起始的分子模型。
The lytic bacteriophage T4 uses multiple mechanisms to initiate the replication of its DNA. Initiation occurs predominantly at replication origins at early times of infection, but there is a switch to genetic recombination-dependent initiation at late times of infection. The T4 insertion-substitution system was used to create a deletion in the T4 dda gene, which encodes a 5'-3' DNA helicase that stimulates both DNA replication and recombination reactions in vitro. The deletion caused a delay in T4 DNA synthesis at early times of infection, suggesting that the Dda protein is involved in the initiation of origin-dependent DNA synthesis. However, DNA synthesis eventually reached nearly wild-type levels, and the final number of phages produced per bacterium was similar to that of the wild type. When the dda mutant phage also contained a mutation in T4 gene 59 (a gene normally required only for recombination-dependent DNA replication), essentially no DNA was synthesized. Recent in vitro studies have shown that the gene 59 protein loads a component of the primosome, the T4 gene 41 DNA helicase, onto DNA. A molecular model for replication initiation is presented that is based on our genetic data.