Question

Poliovirus requires at least one viral-encoded enzyme to replicate. What is this one enzyme required by poliovirus and why must this enzyme be encoded by the virus?

Answer 1

Poliovirus infects human cells by binding to an immunoglobulin-like receptor, CD155 (also known as the poliovirus receptor or PVR) on the cell surface.Interaction of poliovirus and CD155 facilitates an irreversible conformational change of the viral particle necessary for viral entry.

Poliovirus is a positive-stranded RNA virus. Thus, the genome enclosed within the viral particle can be used as messenger RNA and immediately translated by the host cell. On entry, the virus hijacks the cell's translation machinery, causing inhibition of cellular protein synthesis in favor of virus-specific protein production. Unlike the host cell's mRNAs, the 5' end of poliovirus RNA is extremely long—over 700 nucleotides—and highly structured. This region of the viral genome is called internal ribosome entry site(IRES), and it directs translation of the viral RNA. Genetic mutations in this region prevent viral protein production. The first IRES to be discovered was found in poliovirus RNA.