Skirball Institute of Biomolecular Medicine, Department of Cell Biology, NYU School of Medicine, New York, NY 10016, USA.
Structure et Instabilité des Génomes, Muséum National d'Histoire Naturelle, INSERM U 1154, CNRS UMR 7196, 75005 Paris, France; Genome Dynamics in the Immune System Laboratory, INSERM, UMR 1163, Institut Imagine, 75015 Paris, France.
Mol Cell. 2017 Feb 2;65(3):527-538.e6. doi: 10.1016/j.molcel.2016.12.014. Epub 2017 Jan 19.
Mutations in mtDNA lead to muscular and neurological diseases and are linked to aging. The most frequent aberrancy is the "common deletion" that involves a 4,977-bp region flanked by 13-bp repeats. To investigate the basis of this deletion, we developed a single-molecule mtDNA combing method. The analysis of replicating mtDNA molecules provided in vivo evidence in support of the asymmetric mode of replication. Furthermore, we observed frequent fork stalling at the junction of the common deletion, suggesting that impaired replication triggers the formation of this toxic lesion. In parallel experiments, we employed mito-TALENs to induce breaks in distinct loci of the mitochondrial genome and found that breaks adjacent to the 5' repeat trigger the common deletion. Interestingly, this process was mediated by the mitochondrial replisome independent of canonical DSB repair. Altogether, our data underscore a unique replication-dependent repair pathway that leads to the mitochondrial common deletion.
线粒体 DNA 突变导致肌肉和神经疾病，并与衰老有关。最常见的异常是“常见缺失”，涉及侧翼为 13 个碱基重复的 4977 个碱基对区域。为了研究这种缺失的基础，我们开发了一种单分子线粒体 DNA 梳理方法。对复制中的 mtDNA 分子的分析提供了支持不对称复制模式的体内证据。此外，我们观察到在常见缺失连接处频繁出现叉停顿，表明复制受损会触发这种毒性损伤的形成。在平行实验中，我们使用 mito-TALENs 在线粒体基因组的不同位置诱导断裂，发现靠近 5'重复的断裂会触发常见缺失。有趣的是，这个过程是由线粒体复制体介导的，而不依赖于经典的 DSB 修复。总之，我们的数据强调了一种独特的依赖复制的修复途径，导致线粒体常见缺失。
