RNA replication: required intermediates and the dissociation of template, product, and Q.beta. replicase

Abstract

Replication complexes containing only 1 molecule of [phage] Q.beta. replicase and 1 strand of midivariant RNA (MDV-1 RNA) template were prepared by incubating the replicase with an excess of MDV-1 (-) RNA. In the presence of excess minus strands, these monoenzyme replication complexes synthesized essentially pure MDV-1 (+) RNA in both the 1st and 2nd cycles of replication. When an equivalent concentration of mutant MDV-1 (-) RNA was added to this reaction before completion of the 1st cycle of replication, only wild-type MDV-1 (+) RNA was produced in the 1st cycle, but both mutant and wild-type MDV-1 (+) RNA were produced in the 2nd cycle of replication. These results demonstrate that a monenzyme complex is competent to synthesize RNA and that a multienzyme replication complex is not a necessary intermediate of replication. The data also imply that after the completion of chain elongation, the product strand is released from the replication complex and that the template and the replicase then dissociate.