MAPK3 and cancer: We performed an in vitro methyltransferase assay using recombinant PRMT1 protein with a variety of recombinant non-histone proteins that are involved in human tumorigenesis, such as INCENP, AURKB, PTEN, ERK1, HRAS and β-catenin, to identify a novel substrate of PRMT1 in human cancer, and found that PRMT1 methylates INCENP (Figure 1A).