Isolation and characterization of preproinsulin mRNA from fetal bovine pancreatic islets

Total polyadenylated RNA prepared from isolated islets of fetal bovine pancreas was physically characterized. Incubation of this poly A+ RNA with a cell-free protein-synthesizing system derived from wheat germ results in the synthesis of insulin-immunoreactive polypeptide identical in size to that described earlier, 11 200 daltons (Lomedico et al. (1977) J. Biol. Chem. 252, 7971--7978). This material comprised approximately 22% of the total 3H-labeled translation products. Compared to poly A+ RNA from the total pancreas, we conclude that islet mRNA is enriched in proinsulin mRNA.