Figure 1

p53 inhibits the transcriptional activity of the IBP promoter. (A) The putative p53-binding site that is located in the promoter region of the IBP gene is shown. The −231 to −222 and −226 to −217 regions contain noncanonical 1/2 sites. (B) Schematic representations of the five promoter-reporter constructs that contained different-length fragments that were cloned into pGL3-basic vector are shown. The promoter-luciferase constructs or the promoterless vector was transiently transfected into HEK293 cells. The luciferase activity was normalised to Renilla luciferase activity that was expressed by pRL-TK and is presented as the mean ± SD of triplicate experiments. (C) HCT116 p53^−/− and HCT116 p53^+/+ cells were transfected with pIV, pV or pGL3-basic respectively. (D) IBP promoter construct pIV or pV was cotransfected with pCMV-p53 or pCMV-p53R175H into HCT116 p53^−/− cells. The cotransfection with the empty pCMV vector serves as a control. The right inset shows the expression of IBP and p53 in infected HCT116 p53^−/− cells. (E) HCT116 p53^−/− cells were infected with Ad-p53 in the progressively increased concentration. (+, 10²; ++, 10⁴; +++,10⁶ plague-forming units). The right inset shows the expression of p53 in infected HCT116 p53^−/− cells. Cells were transfected with the IBP promoter constructs (pI, pIV, pV or −231/-217 deleted pIV).