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

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

In eukaryotic cells, DNA replication and gene transcription occur in the nucleus, whereas protein production occurs in the cytoplasm. The spatial separation of these major processes guarantees cellular transcription and translation with the help of a transport network. The nucleocytoplasmic trafficking network is responsible for transporting nuclear-resident and cytoplasmic-resident proteins between these two compartments. Translation initiation and replication in the cytoplasm depend on some nuclear-resident proteins, and picornaviruses have recently been shown to shut down the nucleocytoplasmic trafficking of cells to promote viral replication. Five nucleoporins (Nups) have been reported to be targets for picornaviral proteins to disrupt macromolecule trafficking through the nuclear pore complex (NPC) ( Figure 5A ). The 2A pro and 3C pro viral proteinases of enteroviruses are responsible for the specific proteolysis of Nup Figure 5B ]. Moreover, the cleavage of Nup 62 is partially induced in vitro by a high concentration of purified HRV 3C [78] . These studies suggest that picornaviruses may normally alter nucleocytoplasmic trafficking to meet the demands of nuclear-resident proteins for viral replication but that they block the export of cellular mRNA.