The complex of phosphorylated SMAD2/3 and SMAD4, bound to FOXO3, binds to the promoter of the CDKN1A gene. The p-2S-SMAD2/3:SMAD4 complex bound to FOXO1 or FOXO4 can probably also bind to the CDKN1A gene promoter. FOXG1 binding to the FOXO:SMAD complex inhibits FOXO:SMAD-mediated upregulation of CDKN1A transcription. FOXG1 plays an important role in sustained proliferation of telencephalic neuroepithelial progenitor cells (Seoane et al. 2004).