title: Insulin-like growth factor II precursor gene organization in relation to insulin gene family.
abstract: The insulin gene family, comprised of insulin, relaxin, insulin-like growth factors I and II (IGF-I and IGF-II) and possibly the beta-subunit of 7S nerve growth factor, represents a group of structurally related polypeptides whose biological functions have diverged. The IGFs, or somatomedins, constitute a class of polypeptides that have a key role in pre-adolescent mammalian growth (see ref. 4 for review). IGF-I expression is regulated by growth hormone and mediates postnatal growth, while IGF-II appears to be induced by placental lactogen during prenatal development. The primary structures of both human IGFs have been determined and are closely related. A polypeptide highly homologous to human IGF-II is secreted by the rat liver cell line, BRL-3A. As this polypeptide, termed multiplication stimulating activity (MSA), differs from human IGF-II by only five amino acid residues, MSA probably represents the rat IGF-II protein. Using molecular cloning techniques, we have isolated cDNA and chromosomal genes coding for the MSA and human IGF-II precursors, respectively. Our data, presented here, indicate that both MSA and human IGF-II are synthesized initially as larger precursor molecules. The deduced preprohormones both have molecular weights (MWs) of 20,100 and contain C-terminal propeptides of 89 amino acid residues, which we have named E-peptides. The organization of the IGF-II precursor gene is discussed in relation to that of other insulin gene family members.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D004247:DNA / Q000302:isolation & purification; D005796:Genes; D006801:Humans; D007328:Insulin / Q000235:genetics*; D007335:Insulin-Like Growth Factor II; D051379:Mice; D009693:Nucleic Acid Hybridization; D014176:Protein Biosynthesis; D011498:Protein Precursors / Q000235:genetics*; D051381:Rats; D011915:Rats, Inbred BUF; D013002:Somatomedins / Q000235:genetics*; D013329:Structure-Activity Relationship
chemical_list: D007328:Insulin; D011498:Protein Precursors; D013002:Somatomedins; C042532:preproinsulin-like growth factor II; D007335:Insulin-Like Growth Factor II; D004247:DNA