Poliovirus RNA Replication

Abstract

The biosynthesis of RNA directed by an RNA template is a reaction that is unique to RNA viruses. Although studies of polio virus RNA synthesis have been conducted in a somewhat intermittent fashion during the past 25 years in several different laboratories, no clear picture has yet emerged regarding the biochemistry of RNA replication for this or any other RNA virus. Upon entry into the cell, the positive strand, infecting RNA genome directs the synthesis of viral proteins which are required for replication of the RNA. The replication process involves first the synthesis of a negative strand RNA molecule; subsequent transcription of this negative strand produces new copies of the positive strand RNA. Historically, the experimental approach initially utilized to analyze the poliovirus RNA replication reaction was enzymological; efforts were made to isolate and purify an RNA-dependent RNA polymerase activity from virus-infected cells. Indeed, at that time, the only tools available for RNA replication studies were biochemical. The biochemistry, however, proved difficult. RNA replication was found to occur in intracellular structures that are tightly associated with or in membranes, and these proved intractable to purification and dissection. Disruption of the membrane structure in order to isolate template or enzyme components often appeared to alter their properties and/or structures. Thus, the initial approach yielded little information about the mechanism of RNA replication, and it has been only quite recently that alternative approaches have been applied.