(b) Glutamine synthetase reporter plasmids carrying mutations in putative FOXO-binding sites were transfected in HEK293 cells together with Renilla and FOXO3(A3) as indicated. Luciferase activity was measured 40 h after transfection. Data are depicted as relative luciferase units (RLU) compared with the control. Shown are mean ± s.e.m. values (n=3) 