Interaction of mutant p53 with p73: A Surface Plasmon Resonance and Atomic Force Spectroscopy study

Background TP53 tumor suppressor gene is mutated in more than 50% of human tumors. Mutated p53 proteins could sequestrate and inactivate p73 reducing the apoptotic and anti-proliferative effects of the transcription factor, and yielding cancer cells more aggressive and chemoresistant. The possibility of using drugs to prevent the mutant p53/p73 complex formation preserving the p73 function, calls for a deeper insight into the molecular and biochemical mechanisms of mutant p53/p73 protein interaction. Methods The kinetics of the mutant p53R175H/p73 complex was investigated with innovative and complementary techniques, operating in real time, in near physiological conditions and without any labeling. Specifically, Atomic Force Spectroscopy and Surface Plasmon Resonance working at single-molecule level and in bulk condition, respectively, were used. Results The two techniques revealed that a stable complex is formed between mutant p53R175H and p73 proteins; the complex being characterized by a high interaction force and a dissociation equilibrium constant in the order of 10^{- 7} M, as expected for specific interactions. No binding was instead observed between p73 and wild type p53. Conclusions Mutant p53R175H protein, unlike wild type p53, can form a stable complex with p73. The mutant p53R175H/p73 protein complex could be a target for innovative pharmaceutical drugs that, by dissociating it or preventing biomolecule interaction thus preserving the p73 function, could enhance the response of cancerous cells carrying mutant p53R175H protein to common chemotherapeutic agents. General significance The kinetic information obtained in vitro may help to design specific pharmaceutical drugs directed against cancerous cells carrying mutant p53 proteins.