Protein methylation and translation: Role of lysine modification on the function of yeast elongation factor 1 alpha

Abstract

Proteins of the translational apparatus, including ribosomal proteins, release factors, and elongation factors, are known to be modified by a large number of methyltransferases in eukaryotic cells. The majority of these methylation reactions occurs at lysine residues. To date, 12 protein lysine methyltransferase involved in these reactions (Efm1–7; Rkm 1–5) have been identified in the yeast Saccharomyces cerevisiae. Of these 12, 5 appear to be specific to elongation factor 1 alpha (EF1A)(Efm1, Efm4–7). Each methyltransferase modifies a specific lysine residue to give mono‐, di‐, and tri‐methyllysine products. Two of these enzymes (Efm4 and Efm5) are highly conserved in nature while the others appear to be fungal specific.In S. cerevisiae the functional implications of lysine methylation are mostly unknown. EF1A's primary function, with its GTP cofactor, is to deliver amino‐acyl tRNA to the A site of the ribosome during translation. Once the correct tRNA is positioned, a conformational change results in the hydrolysis of GTP and its release from the ribosome for another cycle. Studies have also shown the involvement of EF1A in the assembly of ribosomes.Using yeast genetics we have assessed the biological relevance of EF1A lysine methylation on its translational roles using two approaches. The first approach uses site directed mutagenesis to mutate four of the most conserved methylated lysine sites to arginine residues. The second approach involves combinatorial knockouts of the genes that code for each of the five methyltransferases. In each approach, we have then used functional translation assays in yeast to evaluate the physiological impact of the loss of EF1A methylations. We have found that inactivation of multiple methyltransferases can cause a significant reduction of translational fidelity. Additionally, we have shown that the ribosomal assembly function of EF1A does not appear to be affected by the loss of methyltransferase activity. These studies should illuminate why one protein appears to need five different methyltransferases for its functions.Support or Funding InformationThis work is funded by the National Science Foundation Grant MCB‐1714569 and NSF‐LSAMP Bridge to Doctorate Fellowship.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.