STIMULATION OF POLIOVIRUS PROTEINASE 3C(PRO)-RELATED PROTEOLYSIS BY THE GENOME-LINKED PROTEIN VPG AND ITS PRECURSOR 3AB

Purified recombinant poliovirus polypeptide 3AB interacts with 3CD(pro ) and 3D(pol) as shown by coimmunoprecipitation with anti-3D(pol) anti bodies. A consequence of this interaction is an accelerated autoproces sing of 3CD(pro) to produce 3C(pro) and 3D(pol). The activation of 3D( pol) polymerase activity by cleavage of 3CD(pro), a polypeptide that h as no polymerase activity, can be shown by template- and primer-depend ent poly(U) synthesis. Anti-VPg antibodies (VPg = 3B) added to HeLa tr anslation extracts programmed with poliovirion RNA inhibit cleavage of 3CD(pro) whereas addition of purified 3AB or VPg to these translation reactions increases 3CD(pro) processing. 3AB stimulates also 3C(pro)- related proteolysis of 2BC, a poliovirus-specific, nonstructural proce ssing intermediate. In contrast, 3CD(pro)-specific cleavage of the str uctural precursor P1 is inhibited by the addition of 3AB as shown by a decrease in the production of VPO and VP3. These data shed new light on a phenomenon in the regulation of expression of poliovirus genetic information: whereas the proteinase 3CD(pro) is needed for processing of the capsid precursor, the cleavage product of this relatively stabl e precursor is required for RNA replication.