SUMO1 is required for efficient arsenic-induced PML degradation. (A) U2OS PML^−/− + YFP-PML-V WT cells were exposed to 0.4 μM ML792 for 2 h prior to the addition or not of 1 μM arsenic, followed by live-cell imaging over 18 h. Representative fluorescence microscopy images are shown (upper panels), and relative YFP-PML-V body intensity is normalized to time point 0 h for each frame independently and shown graphically (lower panel). Solid lines are average values, and shaded areas represent one SEM (n = 9 fields of view). (B) Immunofluorescence analysis of WT U2OS (SUMO1^+/+) and SUMO1^−/− cells exposed to 1 µM arsenic for 2 h, fixed, and double-stained with DAPI and anti-SUMO1 (Alexa Fluor 488). (C) SUMO1^+/+ (wt) and SUMO1^−/− (KO) U2OS cells were exposed to 1 µM arsenic for the indicated periods before lysis and analysis by immunoblot for PML. (D) PML immunoblot from crude extracts of SUMO1^−/− U2OS cells after exposure to 1 μM arsenic for the indicated times. * Nonspecific background band. Source data are available for this figure: SourceData F8.