Localization of the Q Replicase Recognition Site in MDV-1 RNA

Abstract

Fragments of MDV-1 RNA (a small, naturally occurring template for Qβ replicase) that were missing nucleotides at either their 5′ end or their 3′ end were still able to form a complex with Qβ replicase. By assaying the binding ability of fragments of different length, it was established that the binding site for Q replicase is determined by nucleotide sequences that are located near the middle of MDV-1 RNA. Fragments missing nucleotides at their 5′ end were able to serve as templates for the synthesis of complementary strands, but fragments missing nucleotides at their 3′ end were inactive, indicating that the 3′-terminal region of the template is required for the initiation of RNA synthesis. The nucleotide sequences of both the 3′ terminus and the central binding region of MDV-1 (+) RNA are almost identical to sequences at the 3′ terminus and at an internal region of Qβ (−) RNA.