IL-2 signaling targets FOXP3 through STAT3 and STAT5 proteins. (A) The location of the human FOXP3 gene on chromosome X is illustrated at top of figure. The middle box shows the proximal region of FOXP3 including exons 1 to 4 as obtained from the University of California Santa Cruz genome assembly Web site and corresponds to a segment located between bases 48 870 000 and 48 878 500 (http://genome.ucsc.edu). The degree of interspecies conservation of the DNA within this segment is represented by peak histograms. The bottom box illustrates a segment of the first intron of FOXP3 located between bases 48 873 406 and 48 873 819, which includes 2 consensus STAT-binding motifs (in blue). The red sequence identifies mutations of the 2 STAT-binding sites introduced in the luciferase constructs. (B) Plasmid constructs were generated that contained wild-type (WT) FOXP3 intronic segment encompassing the 2 STAT motifs upstream of the luciferase cDNA or a mutated version of this segment with disrupted STAT elements. WT (▪) as well as mutated constructs () were cotransfected in 293 cells together with a plasmid containing a constitutively activated form of STAT3, STAT3C, or a constitutively activated form of STAT5, STAT5a1^*6. Transcriptional activity was assessed after 24 hours. Error bars indicate SD.