Sumoylation and HDAC1 binding of IKAROS WT and mutant proteins. (A) HEK293T cells were cotransfected with GFP-sumo1 and hemagglutinin (HA)-tagged IKAROS WT or mutant. Protein extracts were immunoprecipitated with anti-HA antibodies and probed with anti-Sumo1 antibodies to see the sumoylation, as well as with anti-HA antibodies to see the immunoprecipitated IKAROS. Arrows near 100 to 200 kDa indicate single or multiple sumoylated IKAROS protein. (B) HEK293T cells were cotransfected with Flag-tagged IKAROS WT or mutant and HA-tagged HDAC1. Protein lysates were immunoprecipitated with antibodies to the Flag epitope. Western blot analysis of the immunoprecipitation (IP) samples with anti-HA (for HDAC1) and anti-Flag (for IKAROS) antibodies is shown. Five percent of the total volume of the whole-cellular lysates used for IP reactions was loaded as input controls. Data shown are representative of 3 independent experiments.