Properties of the Mengovirus and Poliovirus RNA Polymerases

The enzymatic machinery for the manufacture of the genetic material of virus particles has been partially characterized for DNA bacteriophages (Cohen, 1961), but the catalysts necessary for the replication of the nucleic acid of RNA viruses are less well understood. Until recently, it was postulated that the DNA-dependent RNA polymerase might serve this function via an intermediate DNA strand which carried the specificity of the viral RNA. As a corollary, the synthesis of the RNA of mammalian RNA viruses was thought to be nuclear. With the discovery that almost all RNA synthesis is cytoplasmic in cells infected with Mengovirus (Franklin and Rosner, 1962) and the further demonstration that this synthesis is not sensitive to actinomycin (Reich et al., 1962; Franklin and Baltimore, 1962), it became likely that a polymerization reaction independent of DNA was involved, namely, a cytoplasmic RNA-dependent RNA polymerization. Since all cellular RNA synthesis appears to be nuclear...