FIG. 4.

K-bZIP represses K-Rta-mediated transactivation in a sequence-specific manner. Transient reporter assays were performed with 293 cells transiently cotransfected with a Renilla control reporter and another reporter containing the ORF57 promoter or the PAN RNA promoter. The amount of the K-Rta expression vector was kept at 0.25 μg. The amounts of the K-bZIP and K-bZIPΔBR expression vectors are shown in the panels. In all of these assays, the fold activation was determined by measuring the luciferase activity derived from the reporter plasmid after normalization to the Renilla luciferase activity derived from a cotransfected Renilla TK control plasmid. All experiments were performed in triplicate, and the total amount of DNA was kept constant by using an empty expression vector. The luciferase activity of the reporter plasmid alone is normalized to a value of 1. K-bZIP alone has no transactivation or repression activity.