Regulation of Synthesis of Hepatic Fatty Acid Synthetase: Polysomal Translation in a Cell-free System

Polysomes were isolated from livers of rats fed various diets and were translated in a protein-synthesizing system derived from cultured Chang liver cells. One of the labeled products was identified as complete subunit(s) of fatty acid synthetase by indirect immunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the solubilized immunoprecipitate. The relative amounts of fatty acid synthetase synthesized by polysomes from livers of rats fed a normal diet, starved rats, and rats starved and refed a fat-free diet for 16 hr were 1, 0.1, and 10, respectively. Induction of synthesis of fatty acid synthetase after fat-free refeeding of starved rats began by 2 hr (3-fold increase over starved animals), was increasing rapidly by 5 hr (19-fold over starved animals), and reached a high level by 16 hr (95-fold over starved and 10-fold over normally fed).