Biochemical analysis of human tRNAHis guanylyltransferase in mitochondrial tRNAHis maturation
Biochemical analysis of human tRNAHis guanylyltransferase in mitochondrial tRNAHis maturation
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DOI：
10.1016/j.bbrc.2018.07.150
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发表时间：
2018-09-10
影响因子：
3.1
通讯作者：
Komatsu, Yasuo
中科院分区：
文献类型：
--
作者：
Nakamura, Akiyoshi;Wang, Daole;Komatsu, Yasuo
线粒体含有其自身的蛋白质合成机制，其包括线粒体tRNA成熟。哺乳动物线粒体tRNA（His）（mtDNA（His））是通过在转录后添加1位鸟苷（G（-1））而成熟的，鸟苷是线粒体组氨酰-tRNA合成酶的身份元件。然而，哺乳动物mtDNA（His）的确切成熟过程仍不清楚。在细胞质tRNA（His）（ctRNA（His））成熟中，tRNA（His）鸟苷酰转移酶（Thg 1）将GTP添加到ctRNA（His）的5 '末端，然后去除5'-焦磷酸，以产生成熟的5 '-单磷酸化的G（-1）-ctRNA（His）（pG（-1）-ctRNA（His））。虽然哺乳动物Thg 1定位于细胞质和线粒体，但仍不清楚哺乳动物Thg 1是否在线粒体中的mtDNA（His）成熟中起作用。在这里，我们证明了人Thg 1（hThg 1）通过识别反密码子催化人ctRNA（His）和mtDNA（His）的G（-1）加成反应。虽然hThg 1在体外催化连续的GTP加成到mtDNA（His）上，但它对成熟的pG（-1）-mtDNA（His）没有表现出任何活性。我们进一步发现，hThg 1可以以模板依赖的方式将GMP直接添加到mtDNA（His）的5 '末端，而真菌Thg 1不能。因此，我们推测，在G（-1）加成反应之前或之后，焦磷酸盐去除活性的加速是hThg 1在人类线粒体中维持正常的mtDNA（His）5 '末端的关键特征。这项研究为人类细胞质和线粒体中tRNA（His）成熟之间的差异提供了新的见解。(C)2018爱思唯尔公司All rights reserved.
Mitochondria contain their own protein synthesis machinery, which includes mitochondrial tRNA maturation. It has been suggested that mammalian mitochondrial tRNA(His) (mtRNA(His)) is matured by post-transcriptional addition of guanosine at the 1 position (G(-1)), which serves as an identity element for mitochondrial histidyl-tRNA synthetase. However, the exact maturation process of mammalian mtRNA(His) remains unclear. In cytoplasmic tRNA(His) (ctRNA(His)) maturation, tRNA(His) guanylyltransferase (Thg1) adds a GTP onto the 5'-terminal of ctRNA(His) and then removes the 5'-pyrophosphate to yield the mature 5'-monophospholylated G(-1)-ctRNA(His) (pG(-1)-ctRNA(His)). Although mammalian Thg1 is localized to both the cytoplasm and mitochondria, it remains unclear whether mammalian Thg1 plays a role in mtRNA(His) maturation in mitochondria. Here, we demonstrated that human Thg1 (hThg1) catalyzes the G(-1) addition reaction for both human ctRNA(His) and mtRNA(His) through recognition of the anticodon. While hThg1 catalyzed consecutive GTP additions to mtRNA(His) in vitro, it did not exhibit any activity toward mature pG(-1)-mtRNA(His). We further found that hThg1 could add a GMP directly to the 5'-terminal of mtRNA(His) in a template-dependent manner, but fungal Thg1 could not. Therefore, we hypothesized that acceleration of the pyrophosphate removal activity before or after the G(-1) addition reaction is a key feature of hThg1 for maintaining a normal 5'-terminal of mtRNA(His) in human mitochondria. This study provided a new insight into the differences between tRNA(His) maturation in the cytoplasm and mitochondria of humans. (C) 2018 Elsevier Inc. All rights reserved.