Organization and expression of the chum salmon insulin-like growth factor II gene.

IGF-II plays an important role in growth and development of vertebrates. In the present study, the characterization of the first fish IGF-II gene, chum salmon IGF-II, is described. The sIGF-II gene consists of four exons, spanning a region of 9 kbp, that encode the 214 aa IGF-II precursor. While the amino acid sequences of fully processed IGF-II of salmon and mammalian species are very similar, the prepro-peptide sequence deviates extensively in the signal- and E-peptide domains. The transcription initiation site of the sIGF-II gene was localized within a 30 nt region employing RT-PCR. Using sIGF-II promoter-luciferase constructs it was demonstrated that the sIGF-II gene has a relatively strong promoter that contains tissue-specific regulatory elements.