MODEL OF TRANSLATIONAL CONTROL INVOLVING MESSENGER RNA-ASSOCIATED PROTEINS IN CHICK EMBRYONIC MUSCLES

Highly purified poly(A)-containing free and polysomal mRNP particles have been isolated by chromatography of subcellular fractions of chick embryonic muscles on oligo-dT-cellulose and elution with low salt buffer at 45°. The free and polysomal mRNP represent two distinct classes of macromolecules, the free particles having a more complex nucleoprotein organization than the polysomal particles. Comparison of the protein moieties of three classes of poly(A)-containing cytoplasmic mRNP - those released from nuclei after in vitro transcription and processing (transported mRNP), the free, and polysomal mRNP - strongly suggests that the majority of the mRNA-associated proteins are exchanged in the cytoplasm during the various functional states of mRNA. A model of translational control involving the participation of mRNA-associated proteins in chick embryonic muscles and by analogy in other differentiated eukaryotic cells is proposed. © 1979 Dr. W. Junk bv Publishers.