Rat IGF-I cDNA's contain multiple 5'-untranslated regions.
DNA sequencing of several independent rat IGF-I cDNA clones has revealed three different 5'-untranslated region sequences which contain multiple, upstream, in-frame initiation codons. Use of these codons could generate N-terminal heterogeneity in IGF-I precursor proteins. One of these 5'-untranslated region sequences contains a 40-bp segment which is an inverted repeat of a region in the common 3'-untranslated region. The ends of the IGF-I mRNA corresponding to this cDNA could form a stable duplex structure. Such a complex could prevent ribosomal access to the AUG codons preceding the coding region for the pre-pro-IGF-I peptide, suggesting the possibility of translational regulation of this form of IGF-I mRNA. The 3'-untranslated region inverted repeat sequence also is present in human and mouse IGF-I cDNA's, and, intriguingly, is more highly conserved than the rest of the 3'-untranslated region.
D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D004247:DNA / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000235:genetics*; D008099:Liver / Q000378:metabolism; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D013002:Somatomedins / Q000235:genetics*
D012333:RNA, Messenger; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D004247:DNA