Resolution of Two Factors required in the Qβ-RNA Polymerase Reaction

Abstract

THE Escherichia coli bacteriophage Qβ contains RNA as its genetic component. Qβ-RNA can be synthesized in vitro in the reaction catalysed by the Qβ-RNA polymerase isolated from Qβ infected E. coli¹. The synthesis of infectious Qβ-RNA requires, in addition to the polymerase, the phage RNA to serve as template, ribonucleoside tri-phosphate substrates, Mg⁺⁺, and a factor fraction obtained from both infected and uninfected E. coli². Previous studies with the factor have suggested that it acts on Qβ-RNA at some early step in the reaction². Although an association of the enzyme and Qβ-RNA occurs in the absence of this factor³, synthesis of the complementary minus strand is not detected. The requirement for this agent in the reaction seems to bear a quantitative relationship to Qβ-RNA but not to enzyme². The factor fraction, furthermore, is not required for enzyme activity when synthetic polymers⁴, minus strands or other RNA molecules³ are used as template. These results suggest that the role of factor is to promote a step in the reaction occurring after association of the enzyme with Qβ-RNA, but before nucleotide polymerization.