TAF6δ interacts physically and functionally with p53. (A) TAF6δ interacts with p53 in vitro. Recombinant purified TAF6α, TAF6δ, or TdT were incubated with immobilized GST-p53. Complexes were washed and retained proteins were analyzed by Western blot. The percentage of retention as quantified by phosphoimager analysis is given at the right. (B) Complexes were washed as in (A) except that the washing buffer contained 600 mM KCl. (C) TAF6δ interacts with p53 in vivo. HCT116 p53 -/- cells were transfected with plasmids expressing TAF6δ and p53. 28 hours post-transfection protein interactions were assayed by co-immunoprecipitation followed by Western blotting with the appropriate antibodies (Materials and Methods). (D) TAF6δ enhances p53-mediated activation of the DUSP1 promoter. HeLa cells were co-transfected with a plasmid expressing the firefly luciferase gene under control of DUSP1 promoter, a plasmid expressing p53 or its mutant R175H or no p53 and various constructs of TAF6. 28 h after transfection, cells were lysed and luciferase activity was measured. Shown are the ratios of relative light unit (RLU) given by cells transfected with p53 relative to cells transfected with p53R175H (black bars) or no p53 (grey bars).