Heteroduplex DNA (hetDNA) is a key molecular intermediate during the repair of mitotic double-strand breaks by homologous recombination, but its relationship to 5′ end resection and/or 3′ end extension is poorly understood. In the current study, we examined how perturbations in these processes affect the hetDNA profile associated with repair of a defined double-strand break (DSB) by the synthesis-dependent strand-annealing (SDSA) pathway. Loss of either the Exo1 or Sgs1 long-range resection pathway significantly shortened hetDNA, suggesting that these pathways normally collaborate during DSB repair. In addition, altering the processivity or proofreading activity of DNA polymerase δ shortened hetDNA length or reduced break-adjacent mismatch removal, respectively, demonstrating that this is the primary polymerase that extends both 3′ ends. Data are most consistent with the extent of DNA synthesis from the invading end being the primary determinant of hetDNA length during SDSA.

异源双链DNA（hetDNA）是通过同源重组修复有丝分裂双链断裂过程中的关键分子中间体，但与5'末端切除和/或3'末端延伸的关系知之甚少。在当前的研究中，我们检查了这些过程中的扰动如何通过与合成相关的链退火（SDSA）途径影响与修复定义的双链断裂（DSB）相关的hetDNA谱。Exo1或Sgs1远程切除途径的缺失均显着缩短了hetDNA，表明这些途径通常在DSB修复过程中协同起作用。另外，改变DNA聚合酶δ的持续性或校对活性分别缩短了hetDNA长度或减少了断裂邻近错配去除，表明这是延伸两个3'端的主要聚合酶。