Effect of ribosomes on the biosynthesis of ribonucleic acid in vitro

A deoxyribonucleoprotein that contains RNA polymerase activity and DNA template has been isolated from Escherichia coli and partially purified by zone sedimentation. This preparation synthesizes RNA in the presence of all four nucleoside triphosphates and in the absence of exogenous DNA; the nascent RNA remains attached to the enzyme—template complex during the polymerization reaction. The addition of ribosomes stimulates the synthesis of RNA; the RNA made in the presence of ribosomes is of higher molecular weight than that made in their absence and a significant portion of the nascent RNA is released from the enzyme—template complex, in the form of RNA-ribosome aggregates. Evidence has been obtained that ribosomes, natural acceptors for the nascent RNA, exert a direct effect on RNA synthesis as a consequence of attachment to the growing chain, and possibly of ribosome movement, but not of protein synthesis-dependent movement of the ribosome along the RNA chain.