George J W, Kreuzer K N
Department of Microbiology, Duke University Medical Center, Durham, North Carolina 27710, USA.
Genetics. 1996 Aug;143(4):1507-20. doi: 10.1093/genetics/143.4.1507.
We investigated double-strand break (dsb) repair in bacteriophage T4 using a physical assay that involves a plasmid substrate with two inverted DNA segments. A dsb introduced into one repeat during a T4 infection induces efficient dsb repair using the second repeat as a template. This reaction is characterized by the following interesting features. First, the dsb induces a repair reaction that is directly coupled to extensive plasmid replication; the repaired/replicated product is in the form of long plasmid concatemers. Second, repair of the dsb site is frequently associated with exchange of flanking DNA. Third, the repair reaction is absolutely dependent on the products of genes uvsX, uvsY, 32, 46, and 59, which are also required for phage genomic recombination-dependent DNA replication. Fourth, the coupled repair/replication reaction is only partly dependent on endonuclease VII (gp49), suggesting that either another Holliday-junction-cleaving activity or an alternate resolution pathway is active during T4 infections. Because this repair reaction is directly coupled to extensive replication, it cannot be explained by the SZOSTAK et al. model. We present and discuss a model for the coupled repair/replication reaction, called the extensive chromosome replication model for dsb repair.
我们使用一种物理分析方法研究了噬菌体T4中的双链断裂（dsb）修复，该方法涉及一个带有两个反向DNA片段的质粒底物。在T4感染过程中引入到一个重复序列中的dsb会利用第二个重复序列作为模板诱导高效的dsb修复。该反应具有以下有趣的特征。首先，dsb诱导一种与广泛的质粒复制直接偶联的修复反应；修复/复制产物为长质粒串联体的形式。其次，dsb位点的修复经常与侧翼DNA的交换相关。第三，修复反应绝对依赖于uvsX、uvsY、32、46和59基因的产物，这些基因也是噬菌体基因组重组依赖性DNA复制所必需的。第四，偶联的修复/复制反应仅部分依赖于核酸内切酶VII（gp49），这表明在T4感染期间，要么另一种Holliday连接切割活性，要么一种替代的分辨率途径是活跃的。由于这种修复反应与广泛的复制直接偶联，因此不能用索斯塔克等人的模型来解释。我们提出并讨论了一种偶联修复/复制反应的模型，称为dsb修复的广泛染色体复制模型。
