Characterisation of the internal ribosome entry site element from avian encephalomyelitis virus (AEV).

Avian encephalomyelitis virus (AEV) is a picornavirus that affects young chickens, quails, pheasants and turkeys. Translation initiation on picornavirus mRNA is cap independent and occurs through a mechanism known as internal initiation, which depends on Internal Ribosome Entry Site (IRES) element within the 5' untranslated region (UTR) of the viral RNA. AEV has been assigned within the Hepatovirus genus and shares protein sequence similarity with hepatitis A virus (HAV). I have demonstrated that the 494 nucleotide 5' UTR of the AEV genome contains an internal ribosome entry site (IRES) element. However, in contrast to the HAV IRES, the AEV IRES functions efficiently in the presence of cleaved eEF4G, suggesting functional differences exist. Characterization of the AEV IRES element revealed that there are remarkable structural and functional similarities between the AEV, flavivirus [especially hepatitis C virus (HCV)] and newly discovered type 4 picornaviras IRES elements, including porcine teschovirus-1 (PTV-1), porcine enterovirus-8 (PEV-8) and simian virus-2. These related IRES elements are generally shorter than other picornaviras IRES elements and are able to directly interact with 40S ribosomal subunits. These results indicate that despite classification of AEV as a Hepatovirus, the AEV IRES element should be grouped into the picornavirus type four IRES elements. Seneca Valley virus-001 (SVV) has recently been isolated from pigs and identified as a member of the Picornaviridae capable of killing tumor cells. Initial analysis of the SVV- 001 5' UTR revealed that it may contain an IRES element highly reminiscent of those of the Flaviviridae, especially classical swine fever virus (CSFV). However, further research is required to fully characterize the SVV-001 IRES element