Fig. 14.2

Genome structure of picornaviruses using the example of poliovirus 1. The viral genome possesses a covalently linked protein (Vpg) at the 5′ terminus and is polyadenylated at its 3′ end. Adjacent to the 5′-terminal Vpg there are RNA sequences that form a cloverleaf-like secondary structure, which is essential for genome replication. IRES indicates the internal ribosome entry site that is necessary for binding of ribosomes to the viral RNA genome. The single open reading frame encodes a large precursor polyprotein that is processed into the distinct viral components (structural proteins, non-structural proteins and enzymes) by the proteolytic activity of 2A, 3CD and 3C proteins. The regions representing the proteases are illustrated in red; red arrows indicate the cleavage sites of the respective proteases