Messenger RNA for hepatic tryptophan oxygenase: its partial purification, its translation in a heterologous cell-free system, and its control by glucocorticoid hormones

Abstract

Messenger RNA from rat liver was partially purified by chromatography on cellulose on the basis of its poly(A) content. Microgram amounts of this RNA stimulate protein synthesis manyfold in a heterologous cell-free system, derived from Krebs ascites cells supplemented with reticulocyte initiation factors. The messenger RNA directs the initiation, synthesis, and release of a product that was identified as complete subunits of hepatic tryptophan oxygenase (EC 1.13.1.12) by immunoprecipitation with monovalent antibodies prepared against homogeneous tryptophan oxygenase and subsequent sodium dodecyl sulfate-polyacrylamide electrophoresis of the solubilized immunoprecipitate. This may represent the first complete translation in a heterologous system of a mammalian messenger RNA coding for an enzyme protein. Analysis of the messenger RNA content of the liver after glucocorticoid administration demonstrates that the hormonally enhanced rate of synthesis of tryptophan oxygenase is accompanied by an increased quantity of its corresponding messenger RNA.