Figure 4.
Impact of DNA binding cooperativity on sequence selectivity of transactivation. (A) Shown are p53 binding sequences that differ from the consensus sequence with respect to the CATG in the core of a half-site (bold) and with respect to spacer length (underlined). (B) Luciferase reporter assays. Single copies of the sequences in (A) were cloned into pGL4.23[luc2/minP] and tested for transactivation by the indicated p53 cooperativity mutants. Firefly luciferase activity was measured 48 hours following co-transfection of 100 ng reporter plasmid and 5 ng p53 expression plasmid (pCMVneo-BamHI) into p53-null H1299 cells. The p53 mutants are shown in the order of increasing DNA binding cooperativity. Mean ± SD. (C) Shown is the maximum p53-induced reporter activation for the different promoter sequences. (D) Shown is the ratio of the reporter activities induced by “EE + RR” (high cooperativity) and “RR” (low cooperativity) for the different promoter sequences.