Replication of partial double-stranded RNAs by Qβ replicase

Qβ replicase, an RNA-dependent RNA polymerase of bacteriophage Qβ, uses single-stranded RNA as a template to synthesize the complementary strand. A single-stranded RNA template may contain rigid secondary structures, such as long stems, intermolecular double-stranded RNA regions. Presently, the effect of the size of such double-stranded regions on the replication of RNA by Qβ replicase is unknown. In this study, we prepared RNA templates hybridized with complementary RNA or DNA strands of various sizes and analyzed their replication by Qβ replicase. We found that Qβ replicase synthesizes the complementary strand as long as the template RNA is hybridized with no more than 200 nt fragments, although the replication amounts were decreased. This is important information to evaluate processivity of Qβ replicase.