Reformation of functional liver polyribosomes from ribosome monomers in the absence of RNA synthesis

The administration to rats of the ethyl analog of methionine, ethionine, results in the rapid decrease in the hepatic concentration of adenosine triphosphate followed by an extensive disaggregation of polysomes to ribosome monomers and a concomitant inhibition of protein synthesis. These effects are readily reversed by the injection of methionine or precursors of adenine nucleotides such as adenine. The reformation of liver polyribosomes in such animals following the administration of adenine plus methionine was found to occur under conditions in which new RNA synthesis was markedly inhibited. Free messenger RNA without attached ribosomes must be capable of remaining functionally active in the liver cytoplasm for many hours.