Biogenesis of poxviruses: inactivation of host DNA polymerase by a component of the invading inoculum particle.

Inhibition of nuclear DNA polymerase activity in cells infected with vaccinia virus parallels the development of a nuclease activity similar to one associated with the virus particles. Both phenomena occur in the absence of protein synthesis, implying that incoming particles are responsible for the effects observed. Experimental evidence is presented indicating that the nuclear DNA polymerase activity is inhibited coincidentally with, and perhaps as a consequence of, the hydrolysis of nascent, single-stranded DNA molecules. Should this interpretation prove to be correct, our observations may have revealed the first instance in virus cytopathology linking the inactivation of a specific host-cell function with an enzyme activity originating from the invading particle.