Inhibition of cellular protein synthesis by vaccinia virus surface tubules

The infection of HEp-2 cells with vaccinia virus results in a rapid and selective inhibition of cellular protein synthesis. This effect appears to be due to a structural component(s) of the infecting virion. Experiments investigating the nature of the inhibitory principle showed that a vaccinia virion component, the surface tubule (ST), inhibits protein synthesis in HEp-2 cells without affecting either RNA or DNA synthesis. Furthermore, ST added to a rabbit reticulocyte cell-free system inhibited the incorporation of radiolabeled amino acids into acid-insoluble protein. ST inhibitory activity was destroyed by heat (56° for 60 min) and by prior incubation with specific anti-ST serum. A decrease in the polyribosome complement of cells exposed to purified ST, with a concomitant increase in the free ribosome pool, suggests that the main effect of tubules on cellular protein synthesis occurs at the level of polypeptide chain initiation.