FIG. 3.

K8 represses the transcription of AP-1 in a CBP-dependent manner. (A) Transient reporter assays were performed in which 293T cells were transiently cotransfected with a reporter gene construct (AP-1 Luc) and K8 expression plasmids CMV2N3T K8, K8(190–237), and K8(1–115). The amounts of expression vectors are shown. In all assays, the fold activation was determined by luciferase activity derived from the reporter after normalizing it to β-Gal activity from a cotransfected RSV β-Gal control plasmid. All experiments were performed at least in triplicate, and the total amount of each expression vector was kept constant. The luciferase activity of AP-1 in the absence of the other expression vectors and TPA induction is normalized to a value of 1. (B) AP-1 reporter assays with induction by c-Fos expression vector instead of TPA. (C) CBP relieves the repression of AP-1 by K8 in a dose-dependent manner, but does not activate the AP-1 promoter. (D) Transient reporter assay with the same reporter and expression vectors in BJAB cell lines.