Posttranslational modification of PML, PR-WT, PR-B/L-mut, and PR-B2-mut induced by SUMO1/Ubc9. (A) HA-tagged PML and SUMO1/Ubc9 (SUMO) expression vectors were transfected into HeLa cells as indicated and incubated with or without As₂O₃ (10μM) for 8 hours. Immunoblot analysis using an anti-HA antibody was carried out. Black arrowheads indicate SUMO-modified PML. (B) Xpress-tagged PR-WT, PR-B/L-mut, or PR-B2-mut was overexpressed in HeLa cells with or without SUMO1/Ubc9 and incubated with or without As₂O₃ (10μM) for 8 hours. Black arrowhead indicates SUMO-modified/dimerized PR-WT (lanes 4-6). Note that the modified bands of PR-B/L-mut and PR-B2-mut were barely detected (lanes 7-12).