Discovery of arginine methylation, phosphorylation and their co-occurrence in condensate-associated proteins in Saccharomyces cerevisiae

ABSTRACT: The formation of condensates in membraneless organelles is thought to be driven by protein phase separation. Arginine methylation and serine/threonine phosphorylation are important in the phase separation process, however these post-translational modifications are often present in intrinsically disordered regions that are difficult to analyse with standard proteomic techniques. Here we use a multi-protease and multi-MS/MS fragmentation approach, coupled with heavy methyl SILAC and phospho- or methyl-peptide enrichment, for the analysis of arginine methylation and serine/threonine phosphorylation, and to understand their co-occurrence in condensate-associated proteins. For Saccharomyces cerevisiae, we report a 50% increase in the known arginine methylproteome, involving 15 proteins that are almost all condensate-associated. Importantly, some of these proteins have arginine methylation on all predicted sites – providing evidence that this modification can be pervasive. We explored whether arginine methylated condensate-associated proteins are also phosphorylated, and found 12 such proteins to carry phosphoserine or phosphothreonine. In Npl3, Ded1 and Ssbp1, single peptides were found to carry both modifications, indicating a co-occurrence in close proximity and on the same protein molecule. We show that these co-modifications occur in regions of disorder and that arginine methylation is typically on basic regions of disorder. For phosphorylation, its association with charged regions of condensate-associated proteins was less consistent, although some regions with multisite phosphorylation sites were strongly acidic. We conclude that arginine-methylated proteins associated with condensates are typically co-modified with protein phosphorylation.

INSTRUMENT(S): Orbitrap Fusion Lumos, Q Exactive

ORGANISM(S): Saccharomyces Cerevisiae (baker's Yeast)

SUBMITTER: Joshua Hamey  

LAB HEAD: Marc Wilkins

PROVIDER: PXD022403 | Pride | 2021-09-17

REPOSITORIES: Pride