Abstract
The step sensitive to DRB (5,6-dichloro-1-beta-D- ribofuranosylbenzimidazole) in vaccinia virus replication has been investigated. Ninety microM-DRB extensively inhibited the yield of vaccinia virus after infection of Ehrlich ascites tumour cells. DRB did not inhibit cytoplasmic vaccinia DNA replication. Cytoplasmic viral RNA synthesis (both early and late) was also apparently unaffected and the virus RNAs thus synthesized were normal sized. The expression of early, intermediate and late proteins was not detectably impaired by DRB in vaccinia virus-infected cells. DRB inhibited vaccinia virus replication at the assembly stage since most of the virus DNA remained in a DNase- sensitive form in the infected cells and the virus was therefore not normally coated with virus proteins.