Museum National d'Histoire Naturelle, 43 rue Cuvier, F-75005 Paris, France; CNRS, UMR7196, 43 rue Cuvier, F-75005 Paris, France; Inserm, U1154, 43 rue Cuvier, F-75005 Paris, France.
Department of Internal Medicine and University of New Mexico Cancer Center, University of New Mexico, Albuquerque, NM 87131, USA.
Mol Cell. 2014 Sep 18;55(6):829-842. doi: 10.1016/j.molcel.2014.08.002. Epub 2014 Sep 4.
Breakpoint junctions of the chromosomal translocations that occur in human cancers display hallmarks of nonhomologous end-joining (NHEJ). In mouse cells, translocations are suppressed by canonical NHEJ (c-NHEJ) components, which include DNA ligase IV (LIG4), and instead arise from alternative NHEJ (alt-NHEJ). Here we used designer nucleases (ZFNs, TALENs, and CRISPR/Cas9) to introduce DSBs on two chromosomes to study translocation joining mechanisms in human cells. Remarkably, translocations were altered in cells deficient for LIG4 or its interacting protein XRCC4. Translocation junctions had significantly longer deletions and more microhomology, indicative of alt-NHEJ. Thus, unlike mouse cells, translocations in human cells are generated by c-NHEJ. Human cancer translocations induced by paired Cas9 nicks also showed a dependence on c-NHEJ, despite having distinct joining characteristics. These results demonstrate an unexpected and striking species-specific difference for common genomic rearrangements associated with tumorigenesis.
在人类癌症中发生的染色体易位的断点连接显示出非同源末端连接（NHEJ）的特征。在小鼠细胞中，易位受规范的 NHEJ（c-NHEJ）组件的抑制，包括 DNA 连接酶 IV（LIG4），并且相反地来自替代的 NHEJ（alt-NHEJ）。在这里，我们使用设计的核酸酶（ZFN、TALEN 和 CRISPR/Cas9）在两条染色体上引入 DSB 以研究人细胞中的易位连接机制。引人注目的是，在 LIG4 或其相互作用蛋白 XRCC4 缺失的细胞中，易位发生了改变。易位连接点具有显著更长的缺失和更多的微同源性，表明是 alt-NHEJ。因此，与小鼠细胞不同，人细胞中的易位是由 c-NHEJ 产生的。由配对的 Cas9 切口诱导的人癌细胞易位也显示出对 c-NHEJ 的依赖性，尽管具有不同的连接特征。这些结果表明，与肿瘤发生相关的常见基因组重排存在出乎意料的、显著的种间特异性差异。
