Myrf can be sumoylated at the three consensus sumoylation motifs in the NTM domain (K123, K208, and K276). (A) Three consensus sumoylation motifs in the NTM domain. (B) Immunoprecipitation with HA beads demonstrated that Myrf N-terminal fragment can be sumoylated in primary OLs. The full blot is shown in Supplementary Figure 3A. (C) Immunoprecipitation with HA beads revealed that K123, K208, and K276 serve as major SUMO acceptors for Myrf in CG4 cells. Further, it showed that Myrf K276 is sumoylated by endogenous SUMOs. The full blots are shown in Supplementary Figure 3B. (D) Immunoprecipitation with HA and FLAG beads revealed that K123, K208, and K276 serve as major SUMO acceptors for Myrf in HEK293FT cells. The full blots are shown in Supplementary Figure 3C. (E) Myrf is sumoylated at K276 by endogenous SUMOs even when it is not overexpressed. Flag-Myrf was transfected into Oli-neu cells in 35 mm dishes. Cell lysates were subject to immunoblot analysis. Myrf K276 sumoylation by endogenous SUMOs is delineated by yellow brackets in the magnified image. To equalize immunoblot signals, the amounts of cell lysates loaded were different, as shown by the α-tubulin immunoblot. The full blots are shown in Supplementary Figure 3D. IB: immunoblotting. IP: immunoprecipitation.