SUMOylation of REGγ occurs on multiple sites. (A) REGγ SUMOylation occurs on multiple sites. GFP-REGγ, GFP-REGγ-6KR, or GFP-REGγ derivatives containing one or combinational mutations were co-expressed with His-SUMO-2 in 293T cells. SUMO conjugates were purified and examined as described in Materials and methods. GFP-REGγ-6KR (lane 2) had markedly reduced SUMO conjugates than GFP-REGγ (lane 1). The 4KR refers to combinational mutations in K6, K12, K110, and K243. The input levels of His-SUMO-2 and GFP-REGγ are shown in the lower panels. (B) Effect of SUMOylation site mutation(s) in cytosolic translocation of REGγ. Flag-REGγ and Flag-REGγ with single or combinatorial K mutation at putative SUMO site(s) were transfected into SENP-1−/− MEF cells. Twenty-four hours after transfection, cytoplasmic localization of transfected REGγ derivatives was examined by immunostaining with anti-DDK (Flag) antibody and scored for statistical analysis. Data are shown as mean ± SD of three independent experiments along with the number of cells counted and percentage of positive cells in the cytoplasm, as well as P values.