Roles of the Picornaviral 3C Proteinase in the Viral Life Cycle and Host Cells

Sun, Di; Chen, Shun; Cheng, Anchun; Wang, Mingshu

Despite the diversity of picornaviruses, their genome structures and translation processes are highly conserved. Picornaviruses are small, non-enveloped viruses containing a single-stranded RNA genome with a length of 7.0-8.5 kb. The viral genome contains one open reading frame that encodes a single polyprotein comprising a structural protein P1 region and non-structural protein P2 and P3 regions. Different from cap-dependent initiation of translation, the 5 1 end of picornavirus genomic RNA is linked to a small viral-encoded protein (VPg), instead of 7-methylguanosine, which is necessary Figure 1 . The entire genome structure of poliovirus (PV) [9] . This RNA genome contains a 5′nontranslated region (NTR), a large open reading frame, a 3′NTR and a poly (A) tail. A small viralencoded protein, 3B (VPg), is linked to the 5′ terminus of the RNA. The 5′NTR consists of a cloverleaf structure and a type II internal ribosome entry site (IRES) . The open reading frame encodes a single polyprotein comprising the structural protein P1 region and the non-structural protein P2 and P3 regions.