Structural and Functional Roles of Daxx SIM Phosphorylation in SUMO Paralog-Selective Binding and Apoptosis Modulation

► A bona fide Daxx SIM, E-I-I-V-L-S-D-S-D, binds to SUMO-1 in a parallel orientation ► Daxx SIM can be phosphorylated by CK2 kinase at Ser-737 and Ser-739 ► Phosphorylation enhances Daxx paralog-selective binding to SUMO-1 over SUMO-2/3 ► SIM phosphorylation is important for Daxx in sensitizing stress-induced apoptosis