Abstract：
Mitochondrial RNA metabolism is suggested to occur in identified compartmentalized foci, i.e. mitochondrial RNA granules (MRGs). Mitochondrial aminoacyl-tRNA synthetases (mito aaRSs) catalyze tRNA charging and are key components in mitochondrial gene expression. Mutations of mito aaRSs are associated with various human disorders. However, the suborganelle distribution, interaction network and regulatory mechanism of mito aaRSs remain largely unknown. Here, we found that all mito aaRSs partly colocalize with MRG, and this colocalization is likely facilitated by tRNA-binding capacity. A fraction of human mitochondrial AlaRS (hmtAlaRS) and hmtSerRS formed a direct complex via interaction between catalytic domains in vivo. Aminoacylation activities of both hmtAlaRS and hmtSerRS were fine-tuned upon complex formation in vitro. We further established a full spectrum of interaction networks via immunoprecipitation and mass spectrometry for all mito aaRSs and discovered interactions between hmtSerRS and hmtAsnRS, between hmtSerRS and hmtTyrRS and between hmtThrRS and hmtArgRS. The activity of hmtTyrRS was also influenced by the presence of hmtSerRS. Notably, hmtSerRS utilized the same catalytic domain in mediating several interactions. Altogether, our results systematically analyzed the suborganelle localization and interaction network of mito aaRSs and discovered several mito aaRS-containing complexes, deepening our understanding of the functional and regulatory mechanisms of mito aaRSs.
摘要：
线粒体RNA代谢被认为发生在确定的分隔病灶中，即线粒体RNA颗粒(MRGs)。线粒体氨酰基-tRNA合成酶(mitoaaRSs)催化tRNA带电并且是线粒体基因表达中的关键组分。mitoaaRS的突变与各种人类疾病有关。然而,亚细胞器分布,MitoaaRS的相互作用网络和调节机制在很大程度上仍然未知。这里,我们发现所有mitoaaRS都与MRG部分共定位，这种共定位可能是由tRNA结合能力促进的。人线粒体AlaRS（hmtAlaRS）和hmtSerRS的一部分通过体内催化结构域之间的相互作用形成直接复合物。在体外形成复合物时,对hmtAlaRS和hmtSerRS的氨基酰化活性进行微调。我们通过免疫沉淀和质谱进一步建立了所有mitoaaRS的全谱相互作用网络，并发现了hmtSerRS和hmtAsnRS之间的相互作用。hmtSerRS和hmtTyrRS之间以及hmtThrRS和hmtArgRS之间。hmtTyrRS的活性也受hmtSerRS存在的影响。值得注意的是,hmtSerRS利用相同的催化结构域介导几种相互作用。总之,我们的结果系统地分析了mitoaaRS的亚细胞器定位和相互作用网络，并发现了几个含mitoaaRS的复合物，加深我们对mitoaRS功能和监管机制的理解。
