Arginine methylation is an epigenetic histone modification that affects transcription, but the role of this post-translational modification in cellular functions remains unclear. In Nature Communications, Acuto and colleagues use isomethionine methyl–SILAC to identify arginine-methylation sites in human peripheral blood T cells. Approximately 1,200 proteins linked to transcription, chromatin remodeling, cytoskeleton remodeling and protein transport, cell metabolism and signaling networks undergo arginine methylation in T cells. Arginine methylation is found on adaptors, kinases and phosphatases linked to proximal TCR signaling, such as SLP-76, PLC-γ1, SHIP-1, SHP-2 and PI(3)K, and on key transcription factors that regulate T cell fate programs, such as Notch1, Foxp3, Bcl-11b, IRF4, T-bet and NF-κB. The activation of T cells induces changes in the methylation stoichiometry in 10% of the arginine-methylated peptides, mostly in proteins involved in mRNA splicing, which suggests that arginine methylation can be dynamic.

Nat. Commun. (7 April 2015) doi:10.1038/ncomms7758