Resolution of Two Factors required in the Q β -RNA Polymerase Reaction

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. coli 1 . 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. coli 2 . Previous studies with the factor have suggested that it acts on Qβ-RNA at some early step in the reaction 2 . Although an association of the enzyme and Qβ-RNA occurs in the absence of this factor 3 , 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 enzyme 2 . The factor fraction, furthermore, is not required for enzyme activity when synthetic polymers 4 , minus strands or other RNA molecules 3 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.