Title: Host Cell Nuclear Involvement in Vaccinia Virus Replication Abstract approved: Redacted for Privacy

It was previously shown that vaccinia virus is unable to complete its replicative cycle in cells that have been subjected to cytochala-sin-B mediated enucleation prior to infection. Likewise, in the presence of the drug a-amanitin, a potent inhibitor of host RNA polymerase II but not of viral transcription, the replication of vaccinia virus is inhibited by approximately 95%. These findings led to the conclusion that active participation of the host cell tra-nscriptional apparatus is required for the production of infectious vaccinia virus progeny. In order to identify the viral gene(s) that interacts with the host cell transcriptional apparatus during viral replication, I isolated and characterized a vaccinia virus mutant (a-27) capable of replicating in the presence of the drug a-amanitin. A biochemical analysis of the replication of a-27 versus wild-type vaccinia virus in the presence and absence of the drug revealed no differences wit