Characterization of the vaccinia virus F8L protein

Vaccinia virus infection dramatically affects the host actin cytoskeleton by inducing disassembly of actin stress fibres and formation of actin tails which propel the virus intra- and intercellularly. The viral factors responsible for these actin rearrangements remain unknown. Sequence analysis reveals significant homology between the vaccinia F8L ORF and the proline repeats of iActA, the protein which initiates actin tail assembly and motility in the bacterial pathogen Listeria ivanovii. We characterized the F8L gene product to examine its possible role in vaccinia rearrangements of the host actin cytoskeleton. F8L is a approximately 8 kDa protein expressed early during infection and is found throughout the cytoplasm, with no discernible association with viral or cellular structures. Furthermore, the F8L deletion strain, WR deltaF8L, forms particles and actin tails indistinguishable from WR. Our observations demonstrate that F8L is not required for vaccinia virus morphogenesis or the actin rearrangements observed during infection.