PV has represented a useful model to gain insight into diverse aspects of molecular biology and gene expression. A number of discoveries concerning animal viruses with RNA genomes were initially made in PV. For example, the presence of uncapped mRNA, the sequencing and development of an infectious cDNA clone, the three-dimensional structure of a virus particle, the discovery of the IRES elements, the synthesis of an infectious virus in a cell-free system, the chemical synthesis of a complete viral genomes, among others, were initially reported in PV [34] [35] [36] [37] [38] . In addition, the first time that eIF4G was found proteolytically cleaved was in PV-infected cells [39] .