Accumulation of methyl-deficient rat liver messenger ribonucleic acid on ethionine administration.

Highly purified poly(adenylic acid)-containing RNA isolated from livers of rats fed 0.25% DL-ethionine in the diet for 7 days accepted methyl groups from S-adenosyl[methyl-3H]methionine, when incubated in vitro with mRNA methyltransferases from vaccinia virus or Ehrlich ascites cells, whereas RNA from control rats had no such activity. Nuclease digestion followed by chromatographic analyses of mRNA methylated in vitro revealed that the methyl groups were incorporated at the 5' end into cap 1 structures (m7GpppNmp...) by the viral enzyme, whereas both cap 0 (m7GpppNp...) and cap 1 (m7Gpppm6Am...) structures were formed by the Ehrlich ascites cell enzymes. The methyl-deficient mRNA isolated from the liver of ethionine-fed rats differed in its translational properties from mRNA isolated from control animals in an in vitro protein synthesizing system from wheat germ.