Discovery and characterization of novel protein methyltransferases in Saccharomyces cerevisiae

Abstract

Protein methylation is emerging as the fourth most prevalent post-translational modification in eukaryotes. Arginine and lysine methylation are implicated in a myriad of biological processes， such as RNA processing and transport, transcriptional control, translation, ribosome biogenesis, signal transduction, DNA repair and cellular differentiation. Although many methyltransferases have been identified, along with their substrate proteins, there is evidence that more methyltransferases and their substrate proteins are yet to be discovered in S. cerevisiae. The predominance of both methylarginine and methyllysine was examined in the yeast proteome with a range of biochemical techniques such as immunoblotting, proteome arrays and tandem mass spectrometry. The substrate pool for Efm2p was expanded to include 103 proteins, with novel sites found on known substrate, elongation factor 2 (Eft1p). A series of approaches were then used to discover new methyltransferases. These included affinity capture agents, bioinformatics analysis using sequence alignment and genetic networks and screening of putative methyltransferase knockouts. These approaches identified several probable protein methyltransferases, of which Yjr129cp was confirmed to be a novel lysine methyltransferase. This protein appears to perform multiple types of methylation on more than one protein, making it unusual in the lysine methyltransferases.