Kimbrough Evelyn M, Nguyen Ha An, Li Haixing, Mattingly Jacob M, Bailey Nevette A, Ning Wei, Gamper Howard, Hou Ya-Ming, Gonzalez Ruben L, Dunham Christine M
Department of Chemistry, Emory University, Atlanta, GA, USA.
Department of Chemistry, Columbia University, New York, NY, USA.
Nat Commun. 2025 Aug 11;16(1):7392. doi: 10.1038/s41467-025-62342-4.
RNA post-transcriptional modifications act by stabilizing the functional conformations of RNA. While their role in messenger RNA (mRNA) decoding is well established, it is less clear how transfer RNA (tRNA) modifications outside the anticodon contribute to tRNA stability and accurate protein synthesis. Absence of such modifications causes translation errors, including mRNA frameshifting. By integrating single-molecule fluorescence resonance energy transfer and cryogenic electron microscopy, we demonstrate that the N-methylguanosine (mG) modification at position 37 of Escherichia coli tRNA is necessary and sufficient for modulating the conformational energy of this tRNA on the ribosome so as to suppress +1 frameshifting otherwise induced by this tRNA. Six structures of E. coli ribosomal complexes carrying tRNA lacking mG37 show this tRNA forms four and even five codon-anticodon base pairs as it moves into the +1 frame, allowing direct visualization of the long-standing hypothesis that a four base pair codon-anticodon can form during +1 frameshifting.
RNA转录后修饰通过稳定RNA的功能构象发挥作用。虽然它们在信使RNA（mRNA）解码中的作用已得到充分证实，但反密码子外的转运RNA（tRNA）修饰如何促进tRNA稳定性和准确的蛋白质合成尚不清楚。缺乏此类修饰会导致翻译错误，包括mRNA移码。通过整合单分子荧光共振能量转移和低温电子显微镜技术，我们证明大肠杆菌tRNA第37位的N-甲基鸟苷（mG）修饰对于调节该tRNA在核糖体上的构象能量是必要且充分的，从而抑制该tRNA否则会诱导的+1移码。携带缺乏mG37的tRNA的大肠杆菌核糖体复合物的六个结构表明，当该tRNA移入+1框架时，它会形成四个甚至五个密码子-反密码子碱基对，从而使长期存在的关于在+1移码过程中可以形成四碱基对密码子-反密码子的假设得以直接可视化。
