Translation of Liver Messenger Ribonucleic Acid in a Messenger-dependent Reticulocyte Cell-free System

Abstract

Abstract An RNA fraction with messenger activity has been isolated from free polysomes of rabbit liver. This liver RNA was translated in a reticulocyte cell-free system, which had been rendered dependent on exogenous messenger RNA by mild ribonuclease treatment. After ribonuclease was removed from the ribosomes, protein synthesis was almost totally dependent on 0.5 m KCl ribosomal wash protein and exogenous RNA isolated from either reticulocyte or liver polysomes. In contrast to reticulocyte RNA, which directed the synthesis of α and β globin chains almost exclusively, liver RNA directed synthesis of polypeptides over a broad range of molecular weights. Little globin chain synthesis was detected with liver RNA. Evidence for the specific synthesis of ferritin was obtained by chemical purification and crystallization of this protein from the cell-free reaction product, by immunoprecipitation of the purified material with a monospecific antibody to rabbit liver ferritin, and by coincident migration of radioactivity with purified ferritin in both polyacrylamide and sodium dodecyl sulfate polyacrylamide gel electrophoresis. Since this highly active, fractionated, reticulocyte cell-free system is capable of translating mRNA fractions from both the liver and the reticulocyte into specific natural proteins, it may be useful in future studies dealing with the regulation of protein synthesis with messenger RNA from various animal sources.