Translational discrimination of mRNAs coding for human insulin-like growth factor II.

Sucrose gradient and Northern analyses were used to study the translational status of endogenous multiple mRNAs encoding the prepropeptide for human insulin-like growth factor II. The results showed that a minor 4.8-kilobase mRNA was exclusively engaged in the synthesis of the prepropeptide on membrane-bound polysomes, whereas a major 6.0-kilobase mRNA was present in a cytoplasmic particle which was stable in EDTA. We conclude that the translational discrimination between the mRNAs is dictated by their different 5'-untranslated regions.