Nucleotide sequence and genomic structure of the chicken insulin-like growth factor-II (IGF-II) coding region

Insulin-like growth factor II (IGF-II) is a mitogenic polypeptide with structural similarity to insulin that appears to be involved in regulating embryonic growth. While mammalian IGF-II proteins and IGF-II genes have been well characterized, little is known about avian IGF-II proteins and the genomic sequences that encode them. In this paper we report the isolation and characterization of chicken IGF-II cDNA and genomic clones. The predicted chicken prepro-IGF-II protein contains 187 residues and comprises a signal peptide (24 residues), IGF-II peptide (67 residues), and C-terminal peptide (96 residues), which share 33, 82, and 25/28% amino acid sequence identity, respectively, with their rat/human counterparts. Like the human and rat IGF-II genes, the chicken IGF-II gene has three coding exons. These are interrupted by introns at similar positions to those found in the human and rat IGF-II genes.