The PV genome is composed of a single-stranded RNA copy of positive polarity of about 7.4 Kb [21, 22] . This RNA molecule is uncapped and contains a poly(A) tail at its 3 end and a single open reading frame, which encodes for a polyprotein of about two thousands amino acid residues. This polyprotein is proteolytically processed giving rise to the mature viral proteins [23] (Figure 1(a) ). Three different cleavages can be distinguished on the viral polyprotein: (i) polysomal cleavages that are produced on the nascent polypeptide chain. The first of these cleavages is catalyzed by 2A pro at its amino terminus separating the P1 precursor that encodes for the structural proteins from the rest of nonstructural polypeptides (Figure 1(b) ). The second cleavage still on polysomes is performed by 3C pro , releasing the P2 precursor (2ABC) from P3 (3ABCD); (ii) cytoplasmic cleavages that are mostly exerted by 3C pro and (iii) hydrolysis of VP0 (VP4-VP2), which is concomitant with the morphogenesis of virus particles [2, 23] . All these hydrolytic events lead to the formation of eleven mature proteins and several precursors such as P1, P2, P3, VP0, VP3, VP1, 2BC, 3AB, and 3CD. This last precursor, 3CD, can be used as substrate by 2A pro or 3C pro . The alternative cleavage carried out by 2A pro renders the mature products 3C and 3D , whereas 3C pro generates the canonical proteins 3C pro and 3D pol . However, the biological significance of this alternative cleavage is obscure because PV mutated at 2A pro -cleavage site on 3CD does not exhibit defects in virus replication [24] .