English: Genome organization and expression of enteroviruses and aphthoviruses. Viral RNA (vRNA) is polyadenylated and covalently linked to a virus-encoded protein (3B) at its 5′ end. Cleavages facilitated by 2Apro of the enteroviruses (black arrow) or by an NPG↓P motif at the C-terminus of 2A of foot-and-mouth disease virus (white arrow) release the P1 and P1-2A proteins, respectively. The leader proteinase Lpro releases itself from the polyprotein by cleavage at its own C-terminus. P2 and P3 polypeptides are precursors of the nonstructural proteins necessary for genome replication. Further polyprotein processing is mediated by 3Cpro (cleavage sites indicated by arrow heads). Processing of 1AB, the precursor of 1A and 1B, is thought to be autocatalytic and occurs in empty capsids or at virion maturation (white diamond).