Transfection of N- or C-terminal deletion mutants of p300 abolished the p300 enhancing effect. (A) Linear schemes show wild-type and deletion mutants. Domains are indicated by arrows. (B) Protein levels of the overexpressed wild-type p300 and its mutants determined by Western blots. (C) COX-2 promoter activities in HFb transfected with wild-type p300 and mutants. Control refers to untransfected HFb. Similar results were detected in RAW 264.7 cells (data not shown). Each bar denotes mean ± SEM of 3 experiments.