Unphosphorylated FOXO1 (Ciechomska et al. 2003) and FOXO3 (Brunet et al. 1999), and possibly FOXO4, can bind to three Forkhead-responsive elements in the promoter of the FASLG gene. The FASLG gene encodes FAS ligand (also known as TNFSF6 or CD95-L), a cytokine that binds the FAS receptor (TNFRSF6) and triggers extrinsic apoptosis pathway. AKT-mediated phosphorylation of FOXO3 prevents binding of FOXO3 to the FASLG promoter (Brunet et al. 1999).