Replication of RNA viruses: X. Replication of a natural 6 s RNA by the Qβ RNA polymerase

Abstract

A small RNA that is replicated in vitro by the Qβ RNA polymerase has been discovered in Qβ phage-infected Escherichia coli. The RNA has a sedimentation coefficient of approximately 6 s. Although it represented a small fraction of the total RNA isolated directly from infected cells, it was the predominant nucleic acid component in a partially purified fraction of the Qβ RNA polymerase. It was not detected in uninfected E. coli. The general requirements of the in vitro reaction with the 6 s RNA as template were similar to those with Qβ RNA except that neither of the two host cell macromolecular factors was required. The RNA product of the reaction was synthesized many-fold in excess of the added template and was indistinguishable from the template in its sedimentation and template properties. The base composition of the product was 30.6% C, 29.4% G, 18.4% A and 21.6% U. It contained GTP (pppGp …) at the 5′-terminus, and had a chain length of approximately 130 nucleotides. The RNA product was highly resistant to RNase although nearest-neighbor analysis did not indicate that a completely double-stranded structure was being replicated. The fact that the 6 s RNA is recognized by the highly specific Qβ RNA polymerase suggests that it has at least some nucleotide sequences in common with Qβ RNA. These observations concerning the structure and template property of this RNA may serve to elucidate the origin and role of the 6 to 7 s RNA commonly found in RNA phage-infected bacteria.