Poster abstracts

Poster number 89 submitted by Srujana Samhita Yadavalli

Resampling and editing of mischarged tRNA prior to translation elongation

Srujana S Yadavalli (Dept of Microbiology, The Ohio State University), Jiqiang Ling (Ohio State Biochemistry Program), Byung Ran So (Dept of Chemistry, The Ohio State University), Karin Musier-Forsyth (Ohio State Biochemistry Program, Dept of Chemistry, and Biochemistry, The Ohio State University), Michael Ibba (Ohio State Biochemistry Program, Dept of Microbiology, and Ohio State RNA Group, The Ohio State University)

Abstract:
Protein synthesis occurs in several steps including formation of aminoacyl-tRNAs by aminoacyl-tRNA synthetases (aaRSs) which are then delivered to the ribosome by the elongation factor-Tu (EF-Tu) for decoding. It is important to maintain low error rates at each stage in order to achieve overall translational accuracy and thereby normal functioning of cells. AaRSs pair tRNAs with the correct amino acids through substrate specificity and editing of incorrect products. In the PheRS system, PheRS is specific for its substrate phenylalanine (Phe) but it is also known to misactivate tRNAPhe with tyrosine (Tyr). Mischarged Tyr-tRNAPhe is hydrolyzed by a post-transfer editing mechanism. It was thought that any aminoacyl-tRNA released from an aminoacyl-tRNA synthetase would be sequestered by EF-Tu and incorporated into ribosomal protein synthesis. Our biochemical studies instead show that aminoacyl-tRNAs can readily dissociate from their ternary complex with EF-Tu and re-associate with AaRSs. In the case of a mischarged species, this enables the AaRS to rectify its mistake via the editing pathway. Through in vitro protein synthesis assays we also show that resampling of mischarged tRNAs by AaRSs contributes greatly to translational fidelity, providing additional quality control prior to translation elongation.

Keywords: Editing, Quality control, translation