The chum salmon IGF-II gene promoter is activated by hepatocyte nuclear factor 3beta

IGF-II plays an important role in growth and development of vertebrates and is highly expressed in adult salmon liver. In the present study, we demonstrate that a liver-enriched transcription factor, hepatocyte nuclear factor 3beta (HNF-3beta), is an activator of the chum salmon IGF-II gene. Multiple binding sites for HNF-3beta were identified within the 5'-UTR using electrophoretic mobility shift assays and mutation of these sites prevents binding of HNF-3beta. In transient transfection assays it was shown that mutation of the HNF-3beta binding sites results in a substantial decrease of HNF-3beta-activated salmon IGF-II gene expression. This is the first identified transcription factor that is functionally involved in the regulation of fish IGF-II expression.