Two insulin-like growth factor I messenger RNAs are expressed in human liver.
Through use of a synthetic oligonucleotide probe, human insulin-like growth factor I (IGF-I) cDNA clones were isolated from a liver library. Two types of cDNAs were defined by restriction enzyme analysis and DNA sequencing. Both encode IGF-I precursors of either 195 or 153 amino acids. The two predicted protein precursors are identical from their amino terminus to a lysine residue 16 codons beyond the IGF-I sequence, and then they diverge. Both cDNAs predict additional unique carboxyl-terminal extension peptides. Since there is only one IGF-I gene in the human genome, the finding of two different cDNAs suggests that alternative RNA processing plays a role in IGF-I gene expression. The functions of the different extension peptides remain to be elucidated.
Rotwein
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D001483:Base Sequence; D004247:DNA / Q000235:genetics; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000235:genetics*; D008099:Liver / Q000378:metabolism*; D009693:Nucleic Acid Hybridization; D011498:Protein Precursors / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics*; D013002:Somatomedins / Q000235:genetics*
D011498:Protein Precursors; D012333:RNA, Messenger; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D004247:DNA