Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA.
Department of Applied Physics, Stanford University, Stanford, CA, USA.
Nat Struct Mol Biol. 2018 Mar;25(3):208-216. doi: 10.1038/s41594-018-0030-z. Epub 2018 Feb 19.
Chemical modifications of mRNA may regulate many aspects of mRNA processing and protein synthesis. Recently, 2'-O-methylation of nucleotides was identified as a frequent modification in translated regions of human mRNA, showing enrichment in codons for certain amino acids. Here, using single-molecule, bulk kinetics and structural methods, we show that 2'-O-methylation within coding regions of mRNA disrupts key steps in codon reading during cognate tRNA selection. Our results suggest that 2'-O-methylation sterically perturbs interactions of ribosomal-monitoring bases (G530, A1492 and A1493) with cognate codon-anticodon helices, thereby inhibiting downstream GTP hydrolysis by elongation factor Tu (EF-Tu) and A-site tRNA accommodation, leading to excessive rejection of cognate aminoacylated tRNAs in initial selection and proofreading. Our current and prior findings highlight how chemical modifications of mRNA tune the dynamics of protein synthesis at different steps of translation elongation.
mRNA 的化学修饰可能调节 mRNA 处理和蛋白质合成的许多方面。最近，核苷酸的 2'-O-甲基化被鉴定为人类 mRNA 翻译区的一种常见修饰，在某些氨基酸的密码子中富集。在这里，我们使用单分子、批量动力学和结构方法表明，mRNA 编码区中的 2'-O-甲基化破坏了在同功 tRNA 选择过程中密码子读取的关键步骤。我们的结果表明，2'-O-甲基化在空间上扰乱了核糖体监测碱基（G530、A1492 和 A1493）与同功密码子-反密码子螺旋的相互作用，从而抑制延伸因子 Tu（EF-Tu）和 A 位 tRNA 容纳的下游 GTP 水解，导致初始选择和校对过程中过多地排斥同功氨酰化 tRNA。我们目前和之前的发现强调了 mRNA 的化学修饰如何在翻译延伸的不同步骤调节蛋白质合成的动力学。
