Department of Biochemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, IL 61801, USA.
Biochemistry. 2012 May 22;51(20):4087-95. doi: 10.1021/bi300497x. Epub 2012 May 14.
In an RNA transcript, the 2'-OH group at the 3'-terminal nucleotide is unique as it is the only 2'-OH group that is adjacent to a 3'-OH group instead of a phosphate backbone. The 2'-OH group at the 3'-terminal nucleotide of certain RNAs is methylated in vivo, which is acheived by a methyltransferase named Hen1 that is mechanistically distinct from other known RNA 2'-O-methyltransferases. In eukaryotic organisms, 3'-terminal 2'-O-methylation of small RNAs stabilizes these small RNAs for RNA interference (RNAi). In bacteria, the same methylation during RNA repair results in repaired RNA resisting future damage at the site of repair. Although the chemistry performed by the eukaryotic and bacterial Hen1 is the same, the mechanisms of how RNA is stabilized as a result of the 3'-terminal 2'-O-methylation are different between the eukaryotic RNAi and the bacterial RNA repair. In this review, I will discuss the distribution of Hen1 in living organisms, the classification of Hen1 into four subfamilies, the structure and mechanism of Hen1 that allows it to conduct RNA 3'-terminal 2'-O-methylation, and the possible evolutionary origin of Hen1 present in bacterial and eukaryotic organisms.
在 RNA 转录本中，3'末端核苷酸的 2'-OH 基团是独特的，因为它是唯一的 2'-OH 基团，与 3'-OH 基团相邻，而不是与磷酸骨架相邻。某些 RNA 分子的 3'末端核苷酸中的 2'-OH 基团在体内被甲基化，这是由一种名为 Hen1 的甲基转移酶实现的，它在机制上与其他已知的 RNA 2'-O-甲基转移酶不同。在真核生物中，小 RNA 的 3'末端 2'-O-甲基化稳定了这些小 RNA，从而促进 RNA 干扰（RNAi）。在细菌中，相同的甲基化在 RNA 修复过程中导致修复后的 RNA 抵抗修复部位未来的损伤。尽管真核生物和细菌 Hen1 执行的化学过程相同，但由于 3'末端 2'-O-甲基化，真核生物 RNAi 和细菌 RNA 修复中 RNA 稳定的机制不同。在这篇综述中，我将讨论 Hen1 在生物体内的分布、Hen1 分为四个亚家族的分类、Hen1 的结构和机制，以及细菌和真核生物中存在的 Hen1 的可能进化起源。
