Factor (F)VII plays a critical role in initiation of coagulation. Several segments within the 5' flanking region of the FVII gene were previously demonstrated to recognize hepatic nuclear proteins, but few have been identified. To identify a regulatory protein binding the nuclear hormone response region (-237 to -200) of the FVII 5' flanking region and demonstrate that the interaction is functional. Electrophoretic mobility shift assays and mutation analysis showed that ARP1, an orphan nuclear hormone receptor, interacted with two regions of the FVII 5' flanking region, the hepatic nuclear factor 4 binding region (-77 to -47) and the nuclear hormone response region (-237 to -200). Transfection experiments demonstrated that reporter gene expression was decreased from vectors including the nuclear hormone response segment compared with that containing only the minimal promoter between positions -109 and +1, and that ARP1 also repressed expression through an interaction with the minimal promoter. These data indicate a role for ARP1 in transcriptional modulation of the FVII gene.