Resolution of two factors required in the Q

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.