| The teschoviruses constitute a recently defined picornavirus genus. Most
of the genome sequence of the porcine teschovirus-1 (PTV) Talfan, a causal
agent of porcine enterovirus encephalitis, and several other strains is
known. We now demonstrate that just 280 nt of the porcine teschovirus type
1 Talfan (PTV-1) 5' untranslated region contains an internal ribosome entry
site (IRES) that functions efficiently in vitro and within mammalian cells.
In toeprinting assays, assembly of 48S preinitiation complexes from purified
components on the PTV-1 IRES was achieved with just 40S ribosomal subunits
plus eIF2 and Met-tRNA (i) (Met). Indeed, a binary complex between 40S
subunits and the PTV-1 IRES is formed. Thus, the PTV-1 IRES has properties
that are entirely different from other picornavirus IRES elements but highly
reminiscent of the hepatitis C virus (HCV) IRES. Comparison between the
PTV-1 IRES and HCV IRES elements revealed islands of high sequence identity
that occur in regions critical for the interactions of the HCV IRES with
the 40S ribosomal subunit and eIF3. Thus, there is significant functional
and structural similarity between the IRES elements from the picornavirus
PTV-1 and HCV, a flavivirus. (Diagnosis Section, Department of Exotic Diseases
TEL +81-42-321-1441) |