Hepatitis C virus internal ribosome entry site

Protein translation of most eukaryotic mRNAs requires association of Met-tRNA, several eukaryotic initiation factors, and GTP with the 40S ribosomal subunit. The ribosome can only bind the capped mRNA after binding the initiator tRNA. Translation of hepatitis C virus (HCV) mRNA is initiated by a different mechanism from the usual 5' cap-binding model. This alternate mechanism relies on the direct binding of the 40S ribosomal subunit by the internal ribosome entry site (IRES) in the 5' UTR of HCV RNA. HCV IRES adopts a complex structure, and may differ significantly from IRES elements identified in picornaviruses. A small number of eukaryotic mRNA have been shown to be translated by internal ribosome entry.