Structural basis for substrate binding and catalytic mechanism of a human RNA:m5C methyltransferase NSun6.
Structural basis for substrate binding and catalytic mechanism of a human RNA:m5C methyltransferase NSun6.
复制标题
人 RNA:m5C 甲基转移酶 NSun6 的底物结合和催化机制的结构基础。
DOI：
10.1093/nar/gkx473
复制
发表时间：
2017-06-20
影响因子：
14.9
通讯作者：
Wang ED
中科院分区：
文献类型：
--
作者：
Liu RJ;Long T;Li J;Li H;Wang ED
摘要5-甲基胞嘧啶（m5 C）修饰的RNA在自然界中普遍存在，并在蛋白质翻译调控、RNA加工和应激反应等生物学过程中发挥重要作用。RNA：m5 C甲基转移酶的异常表达与包括癌症在内的多种人类疾病密切相关。然而，到目前为止，没有RNA结合的RNA：m5 C甲基转移酶的结构信息，阻碍了RNA：m5 C甲基化背后的催化机制的阐明。在这里，我们已经解决了NSun 6的结构，一个人的tRNA：m5 C甲基转移酶，在载脂蛋白的形式和复杂的全长tRNA底物。这些结构显示出结合的tRNA的非典型构象，使得靶胞嘧啶的碱基部分可被酶甲基化。进一步的生化分析揭示了两个保守的半胱氨酸残基对RNA的关键但不同的作用：m5 C甲基化。总的来说，我们第一次解决了RNA：m5 C甲基转移酶的复杂结构，并解决了RNA：m5 C甲基转移酶家族的催化机制，这可能允许针对RNA：m5 C甲基转移酶相关疾病的基于结构的药物设计。
Abstract 5-methylcytosine (m5C) modifications of RNA are ubiquitous in nature and play important roles in many biological processes such as protein translational regulation, RNA processing and stress response. Aberrant expressions of RNA:m5C methyltransferases are closely associated with various human diseases including cancers. However, no structural information for RNA-bound RNA:m5C methyltransferase was available until now, hindering elucidation of the catalytic mechanism behind RNA:m5C methylation. Here, we have solved the structures of NSun6, a human tRNA:m5C methyltransferase, in the apo form and in complex with a full-length tRNA substrate. These structures show a non-canonical conformation of the bound tRNA, rendering the base moiety of the target cytosine accessible to the enzyme for methylation. Further biochemical assays reveal the critical, but distinct, roles of two conserved cysteine residues for the RNA:m5C methylation. Collectively, for the first time, we have solved the complex structure of a RNA:m5C methyltransferase and addressed the catalytic mechanism of the RNA:m5C methyltransferase family, which may allow for structure-based drug design toward RNA:m5C methyltransferase–related diseases.