Oral Presentation 24th Annual Lorne Proteomics Symposium 2019

Methylation throughout the proteome: The methyltransferases tell the story (#18)

Joshua J Hamey 1 , Marc R Wilkins 1
  1. Systems Biology Initiative, School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, Australia

Protein methylation is one of the most widespread post-translational modifications in the eukaryotic cell. It is known to regulate key cellular processes including transcription, chromatin remodeling, signal transduction and RNA splicing. Yet, there remains much to be discovered about the roles of this modification. Central to answering this question are the methyltransferases that catalyse protein methylation. In recent years there has been incredible progress in the discovery of these enzymes, by our lab and others, and in particular in yeast and human. We discovered two yeast enzymes, Efm3 (1) and Efm7 (2), as well as two human enzymes, eEF1A-KMT1 (2) and eEF1A-KMT3 (3), that each methylate specific residues in translation elongation factors. To assist the characterisation of these methyltransferases we developed Methyltransferase Motif Analysis by Mass Spectrometry (MT-MAMS) (4). This technique gives unique insight into the sequence specificity of methyltransferases, providing essential clues to the function and potential therapeutic targeting of these enzymes. Functionally, many of these new enzymes specifically target translation elongation factor 1A (eEF1A), an essential protein involved in protein synthesis, protein degradation and cytoskeletal organization. This has led to the realisation that eEF1A is targeted by more independent methyltransferases than any other protein in eukaryotes (5). Through SILAC-based proteomics, we found that eEF1A methylation is subtle in function, suggesting it may have the role of fine-tuning translation. Recently, we have been systematically exploring the interplay between methylation two other prominent modifications, phosphorylation and acetylation. We have already found evidence that methylation events, such as those on eEF1A, can co-occur with phosphorylation, suggesting that interplay between these modifications may be more common than previously appreciated. Due to the substantial number of methyltransferases discovered in the field recently, the complete set of all yeast methyltransferases and substrate proteins has nearly been uncovered. Investigation of this near-complete yeast methylproteome network provides systems-level insights into the function and evolution of this important modification and the enzymes that catalyse it.

  1. Zhang, L., Hamey, J. J., Hart-Smith, G., Erce, M. A., & Wilkins, M. R. (2014). Elongation factor methyltransferase 3–A novel eukaryotic lysine methyltransferase. Biochemical and Biophysical Research Communications, 451(2), 229-234.
  2. Hamey, J. J., Winter, D. L., Yagoub, D., Overall, C. M., Hart-Smith, G., & Wilkins, M. R. (2016). Novel N-terminal and lysine methyltransferases that target translation elongation factor 1A in yeast and human. Molecular & Cellular Proteomics, 15(1), 164-176.
  3. Hamey, J. J., Wienert, B., Quinlan, K. G., & Wilkins, M. R. (2017). METTL21B Is a Novel Human Lysine Methyltransferase of Translation Elongation Factor 1A: Discovery by CRISPR/Cas9 Knockout. Molecular & Cellular Proteomics, 16(12), 2229-2242.
  4. Hamey, J. J., Separovich, R. J., & Wilkins, M. R. (2018). MT-MAMS: protein methyltransferase motif analysis by mass spectrometry. Journal of proteome research, 17(10), 3485-3491.
  5. Hamey, J. J., & Wilkins, M. R. (2018). Methylation of Elongation Factor 1A: Where, Who, and Why? Trends in Biochemical Sciences, 43(3), 211-223