Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, Universidad de Sevilla, Sevilla, Spain.
PLoS Genet. 2012 Sep;8(9):e1002979. doi: 10.1371/journal.pgen.1002979. Epub 2012 Sep 27.
DNA double-strand break (DSB) repair occurring in repeated DNA sequences often leads to the generation of chromosomal rearrangements. Homologous recombination normally ensures a faithful repair of DSBs through a mechanism that transfers the genetic information of an intact donor template to the broken molecule. When only one DSB end shares homology to the donor template, conventional gene conversion fails to occur and repair can be channeled to a recombination-dependent replication pathway termed break-induced replication (BIR), which is prone to produce chromosome non-reciprocal translocations (NRTs), a classical feature of numerous human cancers. Using a newly designed substrate for the analysis of DSB-induced chromosomal translocations, we show that Mus81 and Yen1 structure-selective endonucleases (SSEs) promote BIR, thus causing NRTs. We propose that Mus81 and Yen1 are recruited at the strand invasion intermediate to allow the establishment of a replication fork, which is required to complete BIR. Replication template switching during BIR, a feature of this pathway, engenders complex chromosomal rearrangements when using repeated DNA sequences dispersed over the genome. We demonstrate here that Mus81 and Yen1, together with Slx4, also promote template switching during BIR. Altogether, our study provides evidence for a role of SSEs at multiple steps during BIR, thus participating in the destabilization of the genome by generating complex chromosomal rearrangements.
DNA 双链断裂 (DSB) 在重复 DNA 序列中的修复常常导致染色体重排的产生。同源重组通常通过一种将完整供体模板的遗传信息转移到断裂分子的机制来确保 DSB 的忠实修复。当只有一个 DSB 末端与供体模板具有同源性时，常规的基因转换无法发生，修复可以被引导到一种依赖重组的复制途径，称为断裂诱导复制 (BIR)，BIR 容易产生染色体非相互易位 (NRTs)，这是许多人类癌症的一个经典特征。使用一种新设计的用于分析 DSB 诱导的染色体易位的底物，我们表明 Mus81 和 Yen1 结构选择性内切酶 (SSEs) 促进 BIR，从而导致 NRTs。我们提出 Mus81 和 Yen1 在链入侵中间体处被招募，以允许复制叉的建立，这是完成 BIR 所必需的。在 BIR 过程中复制模板的切换是该途径的一个特征，当使用散布在基因组中的重复 DNA 序列时，会产生复杂的染色体重排。我们在这里证明 Mus81 和 Yen1 与 Slx4 一起在 BIR 过程中也促进模板切换。总之，我们的研究提供了 SSEs 在 BIR 多个步骤中发挥作用的证据，从而通过产生复杂的染色体重排参与基因组的不稳定性。
