Figure 2. Analysis of the interaction of mutant p53 proteins and of wtp53 with the MYC-PU52 quadruplex structure by EMSA and CD spectroscopy. (A-C) Comparison of the binding affinity of mutant p53 and of wtp53 for the MYC-Pu52 intramolecular quadruplex structure (A), double-stranded (ds) oligonucleotide (Py52/Pu52) (B) and p53CON ds sequence (C). Twenty-five, 50 and 100 ng of wtp53, G245S, R248W and R273H mutant p53 were incubated under binding conditions (see M&M) with ³²P-radiolabeled DNA oligonucleotides and 30 ng competitor DNA. (D) CD spectra of the MYC-Pu52 oligonucleotide (0.5 µM) in 5 mM TRIS-HCl, supplemented with 24 mM KCl, supplemented with mutp53R273H (3 µM) and 24 mM KCl. CD spectra were recorded after 24 h when equilibrium was attained. The dotted line corresponds to the CD spectrum of mutp53 alone (0.5 µM). Strong absorption of protein shifts measurement to shorter wavelength.