RNA takes over DNA repair Damage to DNA genomes is normally thought to be repaired with DNA. Pryor et al. now describe a clear exception (see the Perspective by Modesti). They found that RNA is routinely incorporated during the repair of DNA double-strand breaks through the mammalian nonhomologous end–joining (NHEJ) pathway. In a variety of contexts, including V(D)J recombination and Cas9-induced genome engineering, two “DNA” polymerases specific to NHEJ preferentially added RNA in cells. These RNA additions facilitated the critical step of ligation and were later replaced by DNA to complete the NHEJ repair process. Science, this issue p. 1126; see also p. 1069 Mammalian nonhomologous end joining can resolve a wider variety of chromosome breaks when polymerases introduce ribonucleotides during repair. The nonhomologous end–joining (NHEJ) pathway preserves genome stability by ligating the ends of broken chromosomes together. It employs end-processing enzymes, including polymerases, to prepare ends for ligation. We show that two such polymerases incorporate primarily ribonucleotides during NHEJ—an exception to the central dogma of molecular biology—both during repair of chromosome breaks made by Cas9 and during V(D)J recombination. Moreover, additions of ribonucleotides but not deoxynucleotides effectively promote ligation. Repair kinetics suggest that ribonucleotide-dependent first-strand ligation is followed by complementary strand repair with deoxynucleotides, then by replacement of ribonucleotides embedded in the first strand with deoxynucleotides. Our results indicate that as much as 65% of cellular NHEJ products have transiently embedded ribonucleotides, which promote flexibility in repair at the cost of more fragile intermediates.

中文翻译：

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核糖核苷酸掺入能够通过非同源末端连接修复染色体断裂


RNA 接管 DNA 修复 DNA 基因组的损伤通常被认为可以用 DNA 修复。普赖尔等人。现在描述一个明显的例外（参见Modesti 的观点）。他们发现，在 DNA 双链断裂修复过程中，RNA 通常会通过哺乳动物非同源末端连接 (NHEJ) 途径掺入。在各种情况下，包括 V(D)J 重组和 Cas9 诱导的基因组工程，两种 NHEJ 特异性的“DNA”聚合酶会优先在细胞中添加 RNA。这些 RNA 添加促进了连接的关键步骤，随后被 DNA 取代以完成 NHEJ 修复过程。科学，本期第 14 页。 1126;另见 p. 1069 当聚合酶在修复过程中引入核糖核苷酸时，哺乳动物非同源末端连接可以解决更广泛的染色体断裂。非同源末端连接（NHEJ）途径通过将断裂染色体的末端连接在一起来保持基因组稳定性。它使用末端加工酶（包括聚合酶）来准备连接末端。我们发现，两种这样的聚合酶在 NHEJ 过程中（分子生物学中心法则的一个例外）主要掺入核糖核苷酸，无论是在 Cas9 修复染色体断裂的过程中还是在 V(D)J 重组过程中。此外，添加核糖核苷酸而非脱氧核苷酸可有效促进连接。修复动力学表明，核糖核苷酸依赖性第一链连接之后是用脱氧核苷酸进行互补链修复，然后用脱氧核苷酸替换嵌入第一链中的核糖核苷酸。我们的结果表明，多达 65% 的细胞 NHEJ 产物短暂嵌入了核糖核苷酸，这以更脆弱的中间体为代价提高了修复的灵活性。