Regulation of FOXP3 promoter activity by RUNX1 and RUNX3. (A) Human primary CD4+ cells were transfected with an empty vector (pGL3 Basic), a vector containing the wild-type or mutated FOXP3 promoter region (FOXP3 -511/+176) fused to the luciferase reporter gene together with a GFP, RUNX1, or RUNX3 expression vector. Bars show the mean luciferase activity +/- SE measured as arbitrary light units of three independent experiments. (B) Human primary CD4+ cells were transfected with an empty vector (pGL3 Basic), a vector containing the putative FOXP3 promoter region (FOXP3 -511/+176) fused to the luciferase reporter gene, or with a vector containing the putative FOXP3 promoter region (FOXP3 -511/+176) with single RUNX binding sites mutated (53, 287, or 333) or with the combination of two or three RUNX binding sites mutated (53, 287, or 333) fused to the luciferase reporter gene. Bars show the mean luciferase activity +/- SD measured as arbitrary light units of three independent experiments. 
