Valente William J, Ericson Nolan G, Long Alexandra S, White Paul A, Marchetti Francesco, Bielas Jason H
Translational Research Program, Public Health Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA Medical Scientist Training Program, University of Washington School of Medicine, Seattle, WA 98195, USA Molecular and Cellular Biology Graduate Program, University of Washington, Seattle, WA 98195, USA.
Translational Research Program, Public Health Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA.
Nucleic Acids Res. 2016 Oct 14;44(18):8513-8524. doi: 10.1093/nar/gkw716. Epub 2016 Aug 22.
The accumulation of somatic mitochondrial DNA (mtDNA) mutations contributes to the pathogenesis of human disease. Currently, mitochondrial mutations are largely considered results of inaccurate processing of its heavily damaged genome. However, mainly from a lack of methods to monitor mtDNA mutations with sufficient sensitivity and accuracy, a link between mtDNA damage and mutation has not been established. To test the hypothesis that mtDNA-damaging agents induce mtDNA mutations, we exposed MutaMouse mice to benzo[a]pyrene (B[a]P) or N-ethyl-N-nitrosourea (ENU), daily for 28 consecutive days, and quantified mtDNA point and deletion mutations in bone marrow and liver using our newly developed Digital Random Mutation Capture (dRMC) and Digital Deletion Detection (3D) assays. Surprisingly, our results demonstrate mutagen treatment did not increase mitochondrial point or deletion mutation frequencies, despite evidence both compounds increase nuclear DNA mutations and demonstrated B[a]P adduct formation in mtDNA. These findings contradict models of mtDNA mutagenesis that assert the elevated rate of mtDNA mutation stems from damage sensitivity and abridged repair capacity. Rather, our results demonstrate induced mtDNA damage does not readily convert into mutation. These findings suggest robust mitochondrial damage responses repress induced mutations after mutagen exposure.
体细胞线粒体DNA（mtDNA）突变的积累会导致人类疾病的发病机制。目前，线粒体突变在很大程度上被认为是其严重受损基因组处理不准确的结果。然而，主要由于缺乏以足够的灵敏度和准确性监测mtDNA突变的方法，mtDNA损伤与突变之间的联系尚未建立。为了验证mtDNA损伤剂会诱导线粒体DNA突变这一假设，我们将MutaMouse小鼠连续28天每天暴露于苯并[a]芘（B[a]P）或N-乙基-N-亚硝基脲（ENU），并使用我们新开发的数字随机突变捕获（dRMC）和数字缺失检测（3D）分析法对骨髓和肝脏中的mtDNA点突变和缺失突变进行定量。令人惊讶的是，我们的结果表明，尽管有证据表明这两种化合物都会增加核DNA突变，并且证明B[a]P会在mtDNA中形成加合物，但诱变处理并未增加线粒体点突变或缺失突变的频率。这些发现与mtDNA诱变模型相矛盾，该模型认为mtDNA突变率升高源于损伤敏感性和有限的修复能力。相反，我们的结果表明，诱导的mtDNA损伤不容易转化为突变。这些发现表明，强大的线粒体损伤反应会抑制诱变剂暴露后诱导的突变。
