Poliovirus

As described, the poliovirus genome is translated by cellular ribosomes immediately following uncoating into the cytoplasm. Ribosomes bind to the genome at the IRES structure and produce a single large polyprotein of over 2000 amino acids that is sub- sequently cleaved by the viral protease enzyme, itself part of the full-length polyprotein. Through several cleavage steps, structural and nonstructural virus proteins are released, including the virally encoded RNA polymerase. This enzyme subsequently replicates the viral genome in the cytoplasm, a process that begins at (and is dependent on) the3’ polyadenylated tail.  Replication of genomic RNA produces both partially and fully dsRNA replicative intermediates. The negative-sense RNA strand serves as the template for synthesis of positive-sense RNA molecules, which either act as mRNA for increased virus protein synthesis, or become viral genomes. The viral genome mol- ecules (and possibly the negative-sense RNA templates) are covalently associated with the viral protein VPg at their 5’ end, but it is unclear precisely when the protein becomes associated with newly synthesized RNA molecules. Levels of viral proteins and RNA continue to rise rapidly in infected cells for 1–2 days post infection.