Stohr Bradley A, Kreuzer Kenneth N
Department of Microbiology, Duke University Medical Center, Durham, North Carolina 27710, USA.
Genetics. 2002 Nov;162(3):1019-30. doi: 10.1093/genetics/162.3.1019.
The extensive chromosome replication (ECR) model of double-strand-break repair (DSBR) proposes that each end of a double-strand break (DSB) is repaired independently by initiating extensive semiconservative DNA replication after strand invasion into homologous template DNA. In contrast, several other DSBR models propose that the two ends of a break are repaired in a coordinated manner using a single repair template with only limited DNA synthesis. We have developed plasmid and chromosomal recombinational repair assays to assess coordination of the broken ends during DSBR in bacteriophage T4. Results from the plasmid assay demonstrate that the two ends of a DSB can be repaired independently using homologous regions on two different plasmids and that extensive replication is triggered in the process. These findings are consistent with the ECR model of DSBR. However, results from the chromosomal assay imply that the two ends of a DSB utilize the same homologous repair template even when many potential templates are present, suggesting coordination of the broken ends during chromosomal repair. This result is consistent with several coordinated models of DSBR, including a modified version of the ECR model.
双链断裂修复（DSBR）的广泛染色体复制（ECR）模型提出，双链断裂（DSB）的每一端在链侵入同源模板DNA后通过启动广泛的半保留DNA复制而独立修复。相比之下，其他几种DSBR模型提出，断裂的两端使用仅进行有限DNA合成的单个修复模板以协调的方式进行修复。我们开发了质粒和染色体重组修复测定法，以评估噬菌体T4中DSBR过程中断裂末端的协调性。质粒测定法的结果表明，DSB的两端可以使用两个不同质粒上的同源区域独立修复，并且在此过程中会触发广泛的复制。这些发现与DSBR的ECR模型一致。然而，染色体测定法的结果表明，即使存在许多潜在模板，DSB的两端也利用相同的同源修复模板，这表明染色体修复过程中断裂末端的协调性。这一结果与几种DSBR的协调模型一致，包括ECR模型的一个修改版本。
