Fig. 14.4

Genome replication of picornaviruses. In a first step, the RNA genome is translated (1), leading to the synthesis of a polyprotein, which is processed into the individual protein components by the activity of the proteases 2A and 3C/3CD (2). The protein Vpg, which is subsequently uridylylated, arises during this process (3). Cellular proteins are also needed for this process. The Vpg-pUpU complex attaches to the 3′ terminus of the RNA genome (4), acting as a primer for the synthesis of the negative-sense RNA strand by the viral RNA-dependent RNA polymerase (5), which is also generated by proteolytic processing of the polyprotein. New Vpg-pUpU complexes attach to the 3′ terminus of the newly synthesized negative-sense RNA molecules (6). They function as primers for the synthesis of more RNA molecules (7), which now possess positive-sense polarity (8) and serve both as messenger RNA (mRNA) for further protein synthesis and as viral genomes