THE PROMOTER OF THE SALMON INSULIN-LIKE GROWTH-FACTOR-I GENE IS ACTIVATED BY HEPATOCYTE NUCLEAR FACTOR-1

Hepatocyte nuclear factor 1 (HNF-1) was found to have a potent stimula tory action on the activity of the promoter of the salmon insulin-like growth factor I (IGF-I) gene in transient transfection experiments. T his liver-enriched transcription factor was shown to bind to an elemen t in the proximal region of the promoter with distinct nucleotide sequ ence homology to the HNF-1 consensus binding sequence. Mutating this s equence to a variant no longer capable of HNF-1 binding resulted in th e loss of the stimulatory effect. Since the sequence of the HNF-1 bind ing site is conserved in all mammalian, avian, and amphibian species f rom which the IGF-I promoter sequences have been derived to date, we p ropose that HNF-1 may be an important regulator of IGF-I gene expressi on in all of these species.