New publication in Molecular and Cellular Proteomics

Novel N-terminal and Lysine Methyltransferases That Target Translation Elongation Factor 1A in Yeast and Human*

Joshua J. Hamey‡, Daniel L. Winter‡, Daniel Yagoub‡, Christopher M. Overall§, Gene Hart-Smith‡ and Marc R. Wilkins‡,

Author Affiliations

From the ‡Systems Biology Initiative, School of Biotechnology and Biomolecular Sciences, University of New South Wales, New South Wales, 2052, Australia;
§Centre for Blood Research, Departments of Oral Biological and Medical Sciences/Biochemistry and Molecular Biology, University of British Columbia, British Columbia, V6T 1Z4, Canada
? To whom correspondence should be addressed: Tel.: 61 2 9385 3633; Email: m.wilkins@unsw.edu.au.

Abstract

Eukaryotic elongation factor 1A (eEF1A) is an essential, highly methylated protein that facilitates translational elongation by delivering aminoacyl-tRNAs to ribosomes. Here, we report a new eukaryotic protein N-terminal methyltransferase, Saccharomyces cerevisiae YLR285W, which methylates eEF1A at a previously undescribed high-stoichiometry N-terminal site and the adjacent lysine. Deletion of YLR285W resulted in the loss of N-terminal and lysine methylation in vivo, whereas overexpression of YLR285W resulted in an increase of methylation at these sites. This was confirmed by in vitro methylation of eEF1A by recombinant YLR285W. Accordingly, we name YLR285W as elongation factor methyltransferase 7 (Efm7). This enzyme is a new type of eukaryotic N-terminal methyltransferase as, unlike the three other known eukaryotic N-terminal methyltransferases, its substrate does not have an N-terminal [A/P/S]-P-K motif. We show that the N-terminal methylation of eEF1A is also present in human; this conservation over a large evolutionary distance suggests it to be of functional importance. This study also reports that the trimethylation of Lys79 in eEF1A is conserved from yeast to human. The methyltransferase responsible for Lys79methylation of human eEF1A is shown to be N6AMT2, previously documented as a putative N(6)-adenine-specific DNA methyltransferase. It is the direct ortholog of the recently described yeast Efm5, and we show that Efm5 and N6AMT2 can methylate eEF1A from either species in vitro. We therefore rename N6AMT2 as eEF1A-KMT1. Including the present work, yeast eEF1A is now documented to be methylated by five different methyltransferases, making it one of the few eukaryotic proteins to be extensively methylated by independent enzymes. This implies more extensive regulation of eEF1A by this posttranslational modification than previously appreciated.

Footnotes

Author contributions: J.J.H., D.L.W., G.H., and M.R.W. designed the research; J.J.H., D.L.W., and D.Y. performed the research; C.M.O. contributed new reagents or analytic tools; J.J.H. analyzed data; and J.J.H., D.L.W., D.Y., C.M.O., G.H., and M.R.W. wrote the paper.
* This work was supported by various grants. J.J.H., D.L.W. and D.Y. acknowledge the support of Australian Postgraduate Awards. J.J.H. and D.L.W. acknowledge additional support from the University of New South Wales. M.R.W. and G.H.S. acknowledge support from the Australian Research Council. G.H.S. acknowledges additional support from the University of New South Wales. C.M.O. is supported as a Canada Research Chair in Protease Proteomics and Systems Biology.