The 2-thiouridylase function of the human MTU1 (TRMU) enzyme is dispensable for mitochondrial translation
The 2-thiouridylase function of the human MTU1 (TRMU) enzyme is dispensable for mitochondrial translation
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DOI：
10.1093/hmg/ddr397
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发表时间：
2011-12-01
影响因子：
3.5
通讯作者：
Shoubridge, Eric A.
中科院分区：
文献类型：
--
作者：
Sasarman, Florin;Antonicka, Hana;Shoubridge, Eric A.
MTU1 (TRMU) 是一种线粒体酶，负责 tRNA(Lys)、tRNA(Glu) 和 tRNA(Gln) 中摆动 U 的 2-硫醇化，这是一种转录后修饰，被认为对于准确有效地合成 mtDNA 编码的 13 个呼吸链亚基非常重要。 MTU1 突变与急性婴儿肝衰竭有关，这归因于半胱氨酸（硫尿苷化反应的硫供体）的暂时缺乏，导致早期发育过程中线粒体翻译缺陷。据报道，引起锯齿状红纤维肌阵挛性癫痫 (MERRF) 的 tRNA(Lys) 突变也可以阻止摆动 U 的修饰。在这里，我们表明，尽管线粒体 tRNA(Lys)、tRNA(Glu) 和 2-硫醇化严重减少，但 MTU1 患者的成纤维细胞中线粒体翻译未受影响，其中 MTU1 通过免疫印迹检测不到。 tRNA（谷氨酰胺）。我们在这些细胞中观察到的唯一呼吸链异常是复合物 II 组装中间体的积累，然而，这并不影响完全组装的酶的水平。通过 siRNA 介导的 HEK 293 细胞中 MTU1 的敲低观察到相同的表型。此外，线粒体脑肌病、乳酸性酸中毒和中风样发作以及 MERRF 患者的成肌细胞中存在的线粒体翻译缺陷与线粒体 tRNA 转录后修饰缺陷有关，但在这些细胞中敲低 MTU1 后，这些缺陷并未恶化。这项研究表明，在正常稳态 tRNA 水平下，MTU1 不是线粒体翻译所必需的，并且它可能在另一种硫运输途径中具有尚未表征的功能。
MTU1 (TRMU) is a mitochondrial enzyme responsible for the 2-thiolation of the wobble U in tRNA(Lys), tRNA(Glu) and tRNA(Gln), a post-transcriptional modification believed to be important for accurate and efficient synthesis of the 13 respiratory chain subunits encoded by mtDNA. Mutations in MTU1 are associated with acute infantile liver failure, and this has been ascribed to a transient lack of cysteine, the sulfur donor for the thiouridylation reaction, resulting in a mitochondrial translation defect during early development. A mutation in tRNA(Lys) that causes myoclonic epilepsy with ragged-red fibers (MERRF) is also reported to prevent modification of the wobble U. Here we show that mitochondrial translation is unaffected in fibroblasts from an MTU1 patient, in which MTU1 is undetectable by immunoblotting, despite the severe reduction in the 2-thiolation of mitochondrial tRNA(Lys), tRNA(Glu) and tRNA(Gln). The only respiratory chain abnormality that we could observe in these cells was an accumulation of a Complex II assembly intermediate, which, however, did not affect the level of the fully assembled enzyme. The identical phenotype was observed by siRNA-mediated knockdown of MTU1 in HEK 293 cells. Further, the mitochondrial translation deficiencies present in myoblasts from mitochondrial encephalomyopathy, lactic acidosis and stroke-like episode and MERRF patients, which are associated with defects in post-transcriptional modification of mitochondrial tRNAs, did not worsen following knockdown of MTU1 in these cells. This study demonstrates that MTU1 is not required for mitochondrial translation at normal steady-state levels of tRNAs, and that it may possess an as yet uncharacterized function in another sulfur-trafficking pathway.