Human AlkB Homolog ABH8 Is a tRNA Methyltransferase Required for Wobble Uridine Modification and DNA Damage Survival
Human AlkB Homolog ABH8 Is a tRNA Methyltransferase Required for Wobble Uridine Modification and DNA Damage Survival
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DOI：
10.1128/mcb.01604-09
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发表时间：
2010-05-15
影响因子：
5.3
通讯作者：
Samson, Leona D.
中科院分区：
文献类型：
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作者：
Fu, Dragony;Brophy, Jennifer A. N.;Samson, Leona D.
tRNA核苷被广泛修饰以确保其在翻译中的正常功能。然而，哺乳动物中许多负责tRNA修饰的酶还有待鉴定。在这里，我们发现人类AlkB同源物8 （ABH8）催化tRNA甲基化，在某些tRNA的振荡位置产生5-甲基羧甲基尿嘧啶（mcm(5)U），这是一种与DNA损伤存活相关的关键反密码子环修饰。我们发现ABH8与含有mcm(5)U的trna特异性相互作用，纯化的ABH8复合物在体外甲基化RNA。值得注意的是，人类细胞中ABH8的缺失降低了RNA中内源性mcm(5)U的水平，并增加了细胞对dna损伤剂的敏感性。此外，dna损伤剂以atm依赖的方式诱导ABH8表达。这些结果扩展了哺乳动物AlkB蛋白在DNA直接修复之外的作用，并支持了一种涉及tRNA修饰调节的DNA损伤反应途径中的调节机制。
tRNA nucleosides are extensively modified to ensure their proper function in translation. However, many of the enzymes responsible for tRNA modifications in mammals await identification. Here, we show that human AlkB homolog 8 (ABH8) catalyzes tRNA methylation to generate 5-methylcarboxymethyl uridine (mcm(5)U) at the wobble position of certain tRNAs, a critical anticodon loop modification linked to DNA damage survival. We find that ABH8 interacts specifically with tRNAs containing mcm(5)U and that purified ABH8 complexes methylate RNA in vitro. Significantly, ABH8 depletion in human cells reduces endogenous levels of mcm(5)U in RNA and increases cellular sensitivity to DNA-damaging agents. Moreover, DNA-damaging agents induce ABH8 expression in an ATM-dependent manner. These results expand the role of mammalian AlkB proteins beyond that of direct DNA repair and support a regulatory mechanism in the DNA damage response pathway involving modulation of tRNA modification.