Bovine ephemeral fever virus (BEFV) is an arthropod-borne rhabdovirus that is classified as the type species of the genus Ephemerovirus. In addition to the five common rhabdovirus structural proteins (N, P, M, G and L), the large and complex BEFV genome contains several ORFs between the G and L genes (α1, α2/α3, β and γ) encoding proteins of unknown function. We show that the 10.5 kDa BEFV α1 protein is expressed in infected cells and, consistent with previous predictions based on its structure, has the properties of a viroporin. Expression of a BEFVα1-MBP-fusion protein in E. coli was observed to inhibit cell growth and increase membrane permeability to hygromycin-B. In... More
Bovine ephemeral fever virus (BEFV) is an arthropod-borne rhabdovirus that is classified as the type species of the genus Ephemerovirus. In addition to the five common rhabdovirus structural proteins (N, P, M, G and L), the large and complex BEFV genome contains several ORFs between the G and L genes (α1, α2/α3, β and γ) encoding proteins of unknown function. We show that the 10.5 kDa BEFV α1 protein is expressed in infected cells and, consistent with previous predictions based on its structure, has the properties of a viroporin. Expression of a BEFVα1-MBP-fusion protein in E. coli was observed to inhibit cell growth and increase membrane permeability to hygromycin-B. Increased membrane permeability was also observed in BEFV-infected mammalian cells (but not cells infected with an α1-defficient BEFV strain) and in cells expressing a BEFV α1-GFP fusion protein which was shown by confocal microscopy to localize to the Golgi complex. Furthermore, the predicted C-terminal cytoplasmic domain of α1, which contains a strong nuclear localization signal (NLS), was translocated to the nucleus when expressed independently and, in an affinity chromatography assay employing a GFP-trap, the full-length α1 was observed to interact specifically with importin β1 and importin 7, but not with importin α3. These data suggest that, in addition to its function as a viroporin, BEFV α1 may modulate components of nuclear trafficking pathways, but the specific role thereof remains unclear.
