Anti-VPg antibody precipitation of product RNA synthesized in vitro by the poliovirus polymerase and host factor is mediated by VPg on the poliovirion RNA template.

Antibody to the poliovirus genome-linked protein, VPg, specifically immunoprecipitated the product RNA synthesized in vitro by the poliovirus RNA polymerase and HeLa cell host factor when VPg-linked poliovirion RNA was used as a template. The largest product RNA that was immunoprecipitated was twice the size of the template RNA. The complete denaturation of the product RNA with CH3HgOH had no effect on the immunoprecipitation reaction. In contrast, CH3HgOH denaturation prevented the immunoprecipitation of the oligo(U)-primed product RNA. Immunoprecipitation of the product RNA synthesized in the host-factor-dependent reaction was prevented if VPg was removed from the template RNA by pretreatment with proteinase K or if an RNA template without VPg was used in the reaction. The results support our previous evidence that a covalent linkage exists between the labeled negative-strand product RNA and the VPg-linked template RNA and suggest that the purified polymerase and host factor initiated RNA synthesis in vitro in the absence of VPg or a VPg-precursor protein.