Dissociation and Reassociation of Infectious Poliovirus Particles

THE first reconstitution of an infectious virion was achieved when Fraenkel-Conrat and Williams¹ obtained the typical rods of tobacco mosaic virus (TMV) from its components, RNA and protein. Later, the conditions for the “self-assembly” of TMV were improved so that up to 50% of the viral RNA could be coated with the protein. The reconstituted TMV was shown to be infectious and indistinguishable from native virions by several criteria². Recent studies revealed that the reconstitution of TMV is a highly specific multi-step procedure, beginning at the 5′-end of the TMV-RNA^3–5. In the past five years a number of spherical plant viruses have also been reconstituted⁶. In experiments with small RNA-bacteriophages very low efficiencies of reconstitution in the range of 10^–8 to 10^–7 p.f.u. (plaque forming units) per input molecule of RNA were obtained^7,8. Reconstitution was improved by the addition of a minor viral protein, the A-protein, to the mixture of RNA and the structural protein. Even so the efficiency of conversion of RNA into infectious particles was in the range of 2×10^–6 (refs. 9 and 10). We have reported the first successful restoration of poliovirus infectivity lost on dissociation of the virion by urea-mercapto-ethanol treatment¹¹. Here we present evidence for reconstitution of infectious poliovirus particles from a mixture of poliovirus RNA and polypeptides.