Tax undergoes poly-sumoylation on arsenic/interferon exposure. (A) AS/IFN-induced Tax degradation in (upper) HuT-102 and (lower) Tax-transfected HeLa cells. (B) AS/IFN-induced HMW modifications of Tax (bracket) transiently expressed in HeLa cells. (C) AS/IFN-triggered Tax poly-sumoylation detected by immunoprecipitation of Tax transiently expressed in (left) HeLa-SUMO1 or (right) HeLa-SUMO2 cells followed by western blot using indicated antibodies. IgG, isotypic control antibody. (D) Tax-transfected HeLa cells were cotransfected with control siRNA (siCTRL) or siRNA against SUMO1 (siS1), SUMO2&3 (siS2/3), or SUMO1&2&3 (siS1/2/3). Cells were subsequently treated with AS/IFN for 48 hours. Western blot analysis with indicated antibodies. Densitometric quantification of remaining Tax after treatment is shown. (E) (left) Endogenous Tax-SUMO1 interactions detected by Duolink in AS/IFN-treated (12 hours) HuT-102 cells. Nuclei were stained with 4,6 diamidino-2-phenylindole (DAPI; blue). (Right) Graphs show quantification of nuclear or cytoplasmic Duolink dots, indicative of interaction signals. Averages of 1 Z-section per cell from 30 different cells; significant P values are indicated by asterisks. (F) Endogenous Tax-SUMO2/3 interactions in HuT-102 cells, as in E.