Enhancement of the plaque-forming capacity of poliovirus ribonucleic acid with basic proteins.

Smull, Christine E. (The Pennsylvania State University, University Park) and Ernest H. Ludwig. Enhancement of the plaque-forming capacity of poliovirus ribonucleic acid with basic proteins. J. Bacteriol. 84:1035-1040. 1962.-The addition of appropriate amounts of either of two basic proteins to poliovirus ribonucleic acid (RNA) preparations was found to increase markedly the infectivity of the RNA for HeLa cells. These two basic proteins are histone (calf thymus nuclei) and protamine (salmine and clupine). The histone was found to be most effective when used in a final concentration of 200 to 400 mug per ml, and the protamine at approximately 600 mug per ml. The increase in infectivity was brought about in isotonic sodium chloride solution and at neutral pH. An analysis of the period allowed for adsorption of histone-RNA preparations revealed that the greatest increase in infectivity occurred when adsorption was allowed to take place at 4 C for approximately 5 min. An inhibitor of poliovirus RNA infectivity was found in saline washings of the HeLa-cell monolayers, and it was felt that decreased formation or activity of this substance, at 4 C, might account for the increased infectivity of the RNA at 4 C. The addition of RNA and histone to the cell monolayers at separate times resulted in almost no infectivity. The large increase in infectivity was brought about when the RNA and histone were mixed together prior to inoculation on the cell monolayers. A number of other basic materials and two other proteins were found not to increase the infectivity of poliovirus RNA.