Mechanism of tRNA-mediated+1 ribosomal frameshifting

• Type of Material: Article
• Authors: Samuel Hong, Emory University; S. Sunita, Emory University; Tatsuya Maehigashi, Emory University; Eric D. Hoffer, Emory University; Jack A. Dunkle, Emory University; Christine Dunham, Emory University
• Language: English
• Date: 2018-10-30
• Publisher: National Academy of Sciences
• Publication Version: Final Published Version
• Copyright Statement: © 2018 National Academy of Sciences. All rights reserved.
• Final Published Version (URL): http://dx.doi.org/10.1073/pnas.1809319115
• Title of Journal or Parent Work: Proceedings of the National Academy of Sciences
• ISSN: 0027-8424
• Volume: 115
• Issue: 44
• Start Page: 11226
• End Page: 11231
• Grant/Funding Information: This work was supported by National Institutes of Health Grant R01 GM093278.; This research used resources of the Advanced Photon Source, a US Department of Energy Office of Science User Facility operated by Argonne National Laboratory under Contract DE-AC02-06CH11357.; The X-ray crystallography datasets were collected at the Northeastern Collaborative Access Team beamlines, which are funded by National Institute of General Medical Sciences Grant P41 GM103403;and at the Southeast Regional Collaborative Access Team beamlines.; C.M.D. is a Burroughs Wellcome Fund Pathogenesis of Infectious Diseases Fellow.; The Pilatus 6M detector on beamline 24-IDC is funded by National Institutes of Health Office of Research Infrastructure Programs High-End Instrumentation Grant S10 RR029205.
• Keywords: mRNA; Multidisciplinary Sciences; SALMONELLA-TYPHIMURIUM; recoding; PROTEIN-SYNTHESIS; frameshift; STRUCTURAL INSIGHTS; ANTICODON LOOP; TRANSFER-RNA BINDING; MESSENGER-RNA; SUPPRESSOR SUFJ; READING FRAME MAINTENANCE; SITE TRANSFER-RNA; Science & Technology - Other Topics; ribosome; tRNA; GENE-EXPRESSION; Science & Technology
• Research Categories: Chemistry, Biochemistry

Abstract

Accurate translation of the genetic code is critical to ensure expression of proteins with correct amino acid sequences. Certain tRNAs can cause a shift out of frame (i.e., frameshifting) due to imbalances in tRNA concentrations, lack of tRNA modifications or insertions or deletions in tRNAs (called frameshift suppressors). Here, we determined the structural basis for how frameshift-suppressor tRNASufA6 (a derivative of tRNAPro) reprograms the mRNA frame to translate a 4-nt codon when bound to the bacterial ribosome. After decoding at the aminoacyl (A) site, the crystal structure of the anticodon stem-loop of tRNASufA6 bound in the peptidyl (P) site reveals ASL conformational changes that allow for recoding into the +1 mRNA frame. Furthermore, a crystal structure of full-length tRNASufA6 programmed in the P site shows extensive conformational rearrangements of the 30S head and body domains similar to what is observed in a translocation intermediate state containing elongation factor G (EF-G). The 30S movement positions tRNASufA6 toward the 30S exit (E) site disrupting key 16S rRNA-mRNA interactions that typically define the mRNA frame. In summary, this tRNA-induced 30S domain change in the absence of EF-G causes the ribosome to lose its grip on the mRNA and uncouples the canonical forward movement of the tRNAs during elongation.