Studies on cytoplasmic ribonucleic acid from rat liver II. Fractionation and function of microsomal ribonucleic acid

Abstract 1. 1. Rat-liver microsomal RNA isolated by phenol extraction from deoxycholate-insoluble particles was fractionated on the resin Ecteola, yielding at least three fractions. 2. 2. Following in vitro incubation of microsomes with 32 P labelled soluble polynucleotides, AT ATP, GTP, and a nucleoside triphosphate regenerating system, only one microsomal RNA fraction became radioactive. 3. 3. This selective metabolic transfer of soluble RNA (or a derivative thereof) resulted in the attachment to microsomal RNA by covalent bonds. 4. 4. Ribonuclease activity in the ribonucleoprotein particles became manifest after exposure of the particles to 8 M urea. The presence of this enzyme is discussed in connection with the transfer reaction.