ABSTRACT
Foot-and-mouth disease virus (FMDV) is a member of the picornavirus family. The virus has a positive-sense RNA genome that functions like a mRNA and encodes a viral polyprotein. This polyprotein is co-translationally processed, largely by virus encoded proteases, to produce about 15 mature proteins plus many different precursors. These proteins have functions in RNA replication, modification of the host cell and in the assembly of new virus particles. The RNA genome also has to act as the template for RNA replication. This process occurs in two main stages. Initially synthesis of negative strands occurs using the positive strand template and then the production of many positive-sense infectious RNAs is achieved from the negative strands. Some of these infectious RNAs are then packaged by the structural proteins to produce new virus particles. Particular emphasis in this review is placed on the mechanism of protein synthesis initiation on the viral RNA. Early on in FMDV-infected cells, the synthesis of host cell proteins is inhibited, as a result of modifications to the cellular translation machinery that are induced by virus-encoded proteases. However, viral protein synthesis is maintained under these conditions. Initiation of protein synthesis occurs at two different start sites and is directed by a large RNA element of about 450 nt termed the internal ribosome entry site (IRES).
