Transactivation capacity of WT and mutant p53 towards canonical and nncanonical REs.

WT p53 and several structural mutations were examined in three in vivo systems (haploid [1n] and diploid [2n] yeast and human SaOS2 cells) for transactivation from REs representing full, ¾-sites and ½-sites. The ability of the p53, WT or mutant, to transactivate from a RE was measured with a luciferase assay and compared to the ability of WT p53 to transactivate from the p21-5′ RE at 0.008% and 0.024% galactose in 1n and 2n yeast, respectively, or compared to the pGL3 plasmid lacking the promoter REs in human cells. Relative transactivation by a p53 variant in comparison to WT p53 towards the p21-5′ RE is represented by +++ (75–100%), ++ (25–75%), + (7.5–25%), +/− detectable but weak response, or − (no detectable response). The R337C and R337H mutations are compromised for their ability to form tetramers (the equilibrium between dimers and tetramers is altered in comparison to WT p53) [86]. The L344A and L344P mutations result in p53 protein being present as a dimer and monomer, respectively. The Δ368 mutation deletes the C-terminal basic domain required for structure-specific and non-sequence specific binding but has no effect on dimer or tetramer formation. “a” corresponds to significantly higher response at high galactose concentrations (0.128% and 2%). “b” indicates that the mutant was capable of transactivation from RE in an ADE2 plate assay at high galactose concentrations. “d” indicates that the dimer mutation N345S was also analyzed in the mammalian system and yielded the same results as L344A.