Department of Medical Biochemistry and Cell Biology, Institute of Biomedicine, University of Gothenburg, Gothenburg, SE-405 30, Sweden.
Nucleic Acids Res. 2022 Jan 25;50(2):989-999. doi: 10.1093/nar/gkab1251.
Human mitochondria lack ribonucleotide excision repair pathways, causing misincorporated ribonucleotides (rNMPs) to remain embedded in the mitochondrial genome. Previous studies have demonstrated that human mitochondrial DNA polymerase γ can bypass a single rNMP, but that longer stretches of rNMPs present an obstacle to mitochondrial DNA replication. Whether embedded rNMPs also affect mitochondrial transcription has not been addressed. Here we demonstrate that mitochondrial RNA polymerase elongation activity is affected by a single, embedded rNMP in the template strand. The effect is aggravated at stretches with two or more consecutive rNMPs in a row and cannot be overcome by addition of the mitochondrial transcription elongation factor TEFM. Our findings lead us to suggest that impaired transcription may be of functional relevance in genetic disorders associated with imbalanced nucleotide pools and higher levels of embedded rNMPs.
人类线粒体缺乏核苷酸切除修复途径，导致掺入的核糖核苷酸（rNMP）残留在线粒体基因组中。先前的研究表明，人类线粒体 DNA 聚合酶 γ 可以绕过单个 rNMP，但较长的 rNMP 链会阻碍线粒体 DNA 的复制。嵌入的 rNMP 是否也会影响线粒体转录尚未得到解决。在这里，我们证明线粒体 RNA 聚合酶延伸活性受到模板链中单链嵌入 rNMP 的影响。当连续两个或更多个 rNMP 连成一排时，这种影响会加剧，并且添加线粒体转录延伸因子 TEFM 也无法克服。我们的发现表明，转录受损可能与核苷酸池失衡和嵌入 rNMP 水平升高相关的遗传疾病具有功能相关性。
