Fig. 7. A model for the AC-specific lin-3 expression. The AC-specific expression of lin-3, which is essential to induce proper fates of VPCs, is established via an enhancer element (ACEL, 59 bp) that contains two E-boxes and one FTZ-F1 NHR binding site. NHRs activate lin-3 transcription via the FTZ-F1 NHR binding site in the ACEL, which is the site of lin-3(e1417) mutation. HLH-2 binds to both E-boxes in the ACEL and activates the transcription of lin-3 in the AC, which activates the EGF signaling pathway in the VPCs.