Flavivirus E Protein and NS2B Proteinase Quiz

Viral Replication and Translation Processes in Picornaviruses and Flaviviruses

• Picornaviruses use cap-dependent translation mechanism, but infection causes proteolytic cleavage of eIF-4G, hindering host cell translation
• Picornaviruses hijack cellular translation by binding host cell proteins to internal ribosome entry site (IRES)
• Picornavirus proteins are made as a single precursor polyprotein, autocatalytically cleaved into capsid proteins and non-structural proteins
• Replication of picornavirus RNAs occurs in a multiprotein complex bound to cellular vesicles, utilizing negative RNA strand as a template for positive-strand synthesis
• Entry of poliovirus RNA into the cytoplasm involves major conformation changes, leading to virion assembly through cleavage of VP0 to VP2 plus VP4
• Picornavirus infection inhibits host cell functions and leads to the release of newly synthesized virions from the cell
• Flaviviruses are transmitted by arthropods and cause important human diseases, with distinct genome organization resembling Picornaviruses
• The flavivirus virion contains an envelope and 180 copies of M and E (envelope protein heterodimers) arranged with icosahedral symmetry
• Flaviviruses have a linear '+' sense ssRNA genome capped at the 5' end, translated into a single long polyprotein undergoing proteolytic processing
• Flavivirus genome organization is distinct from Togaviruses, despite similar virion morphology and transmission via arthropods
• Flavivirus RNA structures at the 3' end are cleaved into non-structural and structural proteins, including capsid, prM, M, and NS3 proteins
• NS3 protein of Flaviviruses is involved in polyprotein cleavage, RNA replication, and possesses nucleoside triphosphate and helicase activities