SIRT1 deacetylates Foxp3 and decreases its expression. (A) Flag-Foxp3–transfected HEK 293 cells were treated with increasing amounts of TSA (top panel) or NAM (bottom panel) for 16 hours. Foxp3 levels were determined using antibodies against Flag or tubulin as loading control. (B) Cells were cotransfected with Flag-Foxp3 and Myc-SIRT1. Cell lysates were immunoprecipitated using anti-Flag beads and analyzed using anti-Flag or anti-Myc antibodies. (C) Cells were cotransfected with Flag-Foxp3 and Myc-SIRT. Cell lysates were quantified and analyzed by Western blotting using anti-Flag antibody and tubulin as loading control.