tokens: Two plasmids , one containing the amino terminus of P fused to the DNA - binding domain of the yeast transactivator , GAL4 , and the other containing the amino terminus of NP fused to the herpesvirus transactivator , VP16 , were transfected in COS - 1 cells along with a chloramphenicol acetyltransferase ( CAT ) reporter plasmid containing GAL4 DNA - binding sites .