The contribution of conserved functional domains to vhs-dependent RNase activity. The locations of the four boxes (I–IV) in PRV vhs are presented (A). Constructs with deletions of one of the PrV vhs boxes were generated and co-transfected with plasmid expressing luciferase in human 293T cells. Cells transfected with empty vector (pcDNA3.1) or HSV-1 vhs (HSV-1) served as negative and positive controls, respectively. The effects of the individual boxes were evaluated using this in vivo system (luciferase reporter assay). The luciferase activities of three independent assays were plotted (B). In addition, the RNA level of the reporter gene was also monitored by Northern blot analysis (upper panel in C). A loading of total RNA of 10 μg per gel lane was used.