Mrx6 regulates mitochondrial DNA copy number in Saccharomyces cerevisiae by engaging the evolutionarily conserved Lon protease Pim1
Mrx6 regulates mitochondrial DNA copy number in Saccharomyces cerevisiae by engaging the evolutionarily conserved Lon protease Pim1
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DOI：
10.1091/mbc.e19-08-0470
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发表时间：
2020-03-19
影响因子：
3.3
通讯作者：
Walter, Peter
中科院分区：
文献类型：
--
作者：
Goke, Aylin;Schrott, Simon;Walter, Peter
线粒体的功能主要依赖于多个线粒体DNA（mtDNA）拷贝的维持。令人惊讶的是，调节mtDNA拷贝数的细胞机制仍然知之甚少。通过系统的高通量方法在酿酒酵母中，我们确定了5148株缺乏非必需基因的mtDNA与核DNA的比例。筛选结果显示，MRX6是一种基本上没有特征的基因，其缺失导致mtDNA水平显著增加，同时保持野生型线粒体结构和细胞大小。定量超分辨成像显示，MRX6的缺失改变了mtDNA类核的大小和空间分布。我们证明，Mrx6部分共定位与线粒体内的mtDNA和相互作用的保守的Lon蛋白酶Pim 1在一个复杂的，还包括Mam33和Mrx6相关的蛋白质Pet20。Pim 1的急性耗竭表型模仿了在Delta mrx6细胞中观察到的高mtDNA水平。在Delta mrx6细胞中，Pim 1耗尽后没有观察到mtDNA拷贝数的进一步增加，揭示了Pim 1和Mrx6之间的上位关系。人类和细菌Lon蛋白酶通过降解复制起始因子来调节DNA复制，这表明Pim 1与Mrx6复合物的作用类似，提供了一个将其连接到mtDNA的支架。
Mitochondrial function depends crucially on the maintenance of multiple mitochondrial DNA (mtDNA) copies. Surprisingly, the cellular mechanisms regulating mtDNA copy number remain poorly understood. Through a systematic high-throughput approach in Saccharomyces cerevisiae, we determined mtDNA-to-nuclear DNA ratios in 5148 strains lacking nonessential genes. The screen revealed MRX6, a largely uncharacterized gene, whose deletion resulted in a marked increase in mtDNA levels, while maintaining wild type-like mitochondrial structure and cell size. Quantitative superresolution imaging revealed that deletion of MRX6 alters both the size and the spatial distribution of mtDNA nucleoids. We demonstrate that Mrx6 partially colocalizes with mtDNA within mitochondria and interacts with the conserved Lon protease Pim1 in a complex that also includes Mam33 and the Mrx6-related protein Pet20. Acute depletion of Pim1 phenocopied the high mtDNA levels observed in Delta mrx6 cells. No further increase in mtDNA copy number was observed upon depletion of Pim1 in Delta mrx6 cells, revealing an epistatic relationship between Pim1 and Mrx6. Human and bacterial Lon proteases regulate DNA replication by degrading replication initiation factors, suggesting a model in which Pim1 acts similarly with the Mrx6 complex, providing a scaffold linking it to mtDNA.