Cell-free modulation of proinsulin synthesis

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Science  11 Nov 1977:
Vol. 198, Issue 4317, pp. 620-622
DOI: 10.1126/science.918657


In vivo, glucose preferentially stimulates proinsulin biosynthesis; at least part of this process is independent of new RNA synthesis and is accompanied by increases in the overall rate of polypeptide chain initiation. The cell-free translation of proinsulin messenger RNA is very sensitive to changes in the protein-synthesizing system. Proinsulin synthesis is preferentially inhibited by the addition of increasing quantities of polyadenylate-containing RNA from the fetal bovine pancreas or by the addition of the drug, aurintricarboxylic acid, which blocks polypeptide chain initiation. These results suggest that proinsulin messenger RNA completes less efficiently for rate controlling initiation factors. We propose that glucose stimulates proinsulin biosynthesis by allowing the less competitive proinsulin messenger RNA to be translated more efficiently.