Structural insights into translational recoding by frameshift suppressor tRNASufJ

• Type of Material: Article
• Authors: Crystal E. Fagan, Emory University; Tatsuya Maehigashi, Emory University; Jack A. Dunkle, Emory University; Stacey J. Miles, Emory University; Christine M. Dunham, Emory University
• Language: English
• Date: 2014-12
• Publisher: Cold Spring Harbor Laboratory Press
• Publication Version: Final Published Version
• Copyright Statement: © 2014 Fagan et al.
• License: Creative Commons Attribution-NonCommercial 4.0 International
• Final Published Version (URL): https://doi.org/10.1261/rna.046953.114
• Title of Journal or Parent Work: RNA
• Volume: 20
• Issue: 12
• Start Page: 1944
• End Page: 1954
• Grant/Funding Agency: Department of Defense; National Institutes of Health; US Department of Energy
• Grant/Funding Information: Support for this work was provided by the Department of Defense through the National Defense Science and Engineering Graduate Fellowship Program and National Institutes of Health (NIH) Training Grant T32 GM8367 (to C.E.F.), and National Institute of General Medical Sciences of the NIH Award R01GM093278 (to C.M.D.). C.M.D. is a Pew Scholar in the Biomedical Sciences (Pew Charitable Trusts).; Use of the Advanced Photon Source, an Office of Science User Facility operated for the US Department of Energy (DOE) Office of Science by Argonne National Laboratory, was supported by US DOE Contract DE-AC02-06CH11357.
• Keywords: reading frame; X-ray crystal structure; ribosome; decoding; anticodon stem–loop; mRNA
• Subject - Topics: Transfer RNA; Proteins--Synthesis; Ribosomes

Abstract

The three-nucleotide mRNA reading frame is tightly regulated during translation to ensure accurate protein expression. Translation errors that lead to aberrant protein production can result from the uncoupled movement of the tRNA in either the 5′ or 3′ direction on mRNA. Here, we report the biochemical and structural characterization of +1 frameshift suppressor tRNASufJ, a tRNA known to decode four, instead of three, nucleotides. Frameshift suppressor tRNASufJ contains an insertion 5′ to its anticodon, expanding the anticodon loop from seven to eight nucleotides. Our results indicate that the expansion of the anticodon loop of either ASLSufJ or tRNASufJ does not affect its affinity for the A site of the ribosome. Structural analyses of both ASLSufJ and ASLThr bound to the Thermus thermophilus 70S ribosome demonstrate both ASLs decode in the zero frame. Although the anticodon loop residues 34–37 are superimposable with canonical seven-nucleotide ASLs, the single C31.5 insertion between nucleotides 31 and 32 in ASLSufJ imposes a conformational change of the anticodon stem, that repositions and tilts the ASL toward the back of the A site. Further modeling analyses reveal that this tilting would cause a distortion in full-length A-site tRNASufJ during tRNA selection and possibly impede gripping of the anticodon stem by 16S rRNA nucleotides in the P site. Together, these data implicate tRNA distortion as a major driver of noncanonical translation events such as frameshifting.