Nucleotide sequences of cDNAs encoding precursors of human insulin-like growth factor II (IGF-II) and an IGF-II variant.

We have isolated 3 cDNA clones encoding human IGF-II and a variant of IGF-II. The amino acid sequence encoded by the IGF-II cDNA is identical to the sequence previously described [(1978) FEBS Lett. 89, 283-286]. In the amino acid sequence predicted by the IGF-II variant cDNA, the Ser residue 29 in the B-domain has been replaced by an Arg-Leu-Pro-Gly sequence. The corresponding mRNAs probably arise by alternative splicing of a common RNA precursor. The IGF coding region of the cDNA inserts is flanked by sequences encoding a signal peptide and a carboxy-terminal peptide indicating that both human IGF-II and its variant are synthesized as precursors.