Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX, USA.
Department of Cardiology, Boston Children's Hospital, 300 Longwood Avenue, Boston, MA, USA.
Nat Commun. 2024 Sep 3;15(1):7653. doi: 10.1038/s41467-024-52147-2.
In metazoans mitochondrial DNA (mtDNA) or retrotransposon cDNA released to cytoplasm are degraded by nucleases to prevent sterile inflammation. It remains unknown whether degradation of these DNA also prevents nuclear genome instability. We used an amplicon sequencing-based method in yeast enabling analysis of millions of DSB repair products. In non-dividing stationary phase cells, Pol4-mediated non-homologous end-joining increases, resulting in frequent insertions of 1-3 nucleotides, and insertions of mtDNA (NUMTs) or retrotransposon cDNA. Yeast EndoG (Nuc1) nuclease limits insertion of cDNA and transfer of very long mtDNA ( >10 kb) to the nucleus, where it forms unstable circles, while promoting the formation of short NUMTs (~45-200 bp). Nuc1 also regulates transfer of extranuclear DNA to nucleus in aging or meiosis. We propose that Nuc1 preserves genome stability by degrading retrotransposon cDNA and long mtDNA, while short NUMTs originate from incompletely degraded mtDNA. This work suggests that nucleases eliminating extranuclear DNA preserve genome stability.
在后生动物中，线粒体 DNA（mtDNA）或逆转录转座子 cDNA 释放到细胞质中后，会被核酶降解，以防止无菌性炎症。目前尚不清楚这些 DNA 的降解是否也能防止核基因组不稳定。我们使用了一种基于扩增子测序的酵母方法，该方法能够分析数百万个 DSB 修复产物。在非分裂的静止期细胞中，Pol4 介导的非同源末端连接增加，导致 1-3 个核苷酸的频繁插入，以及 mtDNA（NUMTs）或逆转录转座子 cDNA 的插入。酵母内 endoG（Nuc1）核酸酶限制 cDNA 的插入和非常长的 mtDNA（>10kb）向核内的转移，在核内形成不稳定的环，同时促进短 NUMTs（~45-200bp）的形成。Nuc1 还在衰老或减数分裂过程中调节核外 DNA 向核内的转移。我们提出，Nuc1 通过降解逆转录转座子 cDNA 和长 mtDNA 来维持基因组稳定性，而短 NUMTs 则来源于不完全降解的 mtDNA。这项工作表明，消除核外 DNA 的核酶可以维持基因组稳定性。
