Structural insights into mRNA reading frame regulation by tRNA modification and slippery codon-anticodon pairing

• Published in: eLife 2020-10, Vol.9 (2020)
• Main Authors: Hoffer, Eric D, Hong, Samuel, Sunita, S, Maehigashi, Tatsuya, Gonzalez, Jnr, Ruben L, Whitford, Paul C, Dunham, Christine M
• Format: Article
• Language: English
• Subjects: Anticodon - metabolism; BASIC BIOLOGICAL SCIENCES; Biochemistry and Chemical Biology; Codon - metabolism; Escherichia coli - genetics; Escherichia coli - metabolism; fidelity; frameshift; Gene Expression Regulation, Bacterial; mRNA; near-cognate; Nucleotides; Reading Frames - genetics; ribosome; Ribosomes - metabolism; RNA; RNA, Messenger - genetics; RNA, Messenger - metabolism; RNA, Transfer - genetics; RNA, Transfer - metabolism; Structural Biology and Molecular Biophysics; tRNA
• ISSN: 2050-084X; 2050-084X
• DOI: 10.7554/eLife.51898

Modifications in the tRNA anticodon loop, adjacent to the three-nucleotide anticodon, influence translation fidelity by stabilizing the tRNA to allow for accurate reading of the mRNA genetic code. One example is the N1-methylguanosine modification at guanine nucleotide 37 (m G37) located in the anticodon loop andimmediately adjacent to the anticodon nucleotides 34, 35, 36. The absence of m G37 in tRNA causes +1 frameshifting on polynucleotide, slippery codons. Here, we report structures of the bacterial ribosome containing tRNA bound to either cognate or slippery codons to determine how the m G37 modification prevents mRNA frameshifting. The structures reveal that certain codon-anticodon contexts and the lack of m G37 destabilize interactions of tRNA with the P site of the ribosome, causing large conformational changes typically only seen during EF-G-mediated translocation of the mRNA-tRNA pairs. These studies provide molecular insights into how m G37 stabilizes the interactions of tRNA with the ribosome in the context of a slippery mRNA codon.