Several studies indicate that FKHR and AFX, mammalian homologues of the Caenorhabditis elegans forkhead transcription factor DAF-16, function in the insulin signaling pathway promoter contains one IRS, while in the IGFBP-1 promoter two copies of IRS are arranged as an inverted palindrome. Three tandem copies of IRSs are present in the G6Pase. AFX has been recently shown to serve as a substrate of PKB both in vitro and in vivo, and its transcriptional activity is inhibited by phosphorylation.