Experimental kinetic mechanism of P53 condensation-amyloid aggregation.

The tumor suppressor p53 modulates the transcription of a variety of genes, constituting a protective barrier against anomalous cellular proliferation. High-frequency "hotspot" mutations result in loss of function by the formation of amyloid-like aggregates that correlate with cancerous progression. We show that full-length p53 undergoes spontaneous homotypic condensation at submicromolar concentrations and in the absence of crowders to yield dynamic coacervates that are stoichiometrically dissolved by DNA. These coacervates fuse and evolve into hydrogel-like clusters with strong thioflavin T binding capacity, which further evolve into fibrillar species with a clearcut branching growth pattern. The amyloid-like coacervates can be rescued by the human papillomavirus master regulator E2 protein to yield large regular droplets. Furthermore, we kinetically dissected an overall condensation mechanism, which consists of a nucleation-growth process by the sequential addition of p53 tetramers, leading to discretely sized and monodisperse early condensates followed by coalescence into bead-like coacervates that slowly evolve to the fibrillar species. Our results suggest strong similarities to condensation-to-amyloid transitions observed in neurological aggregopathies. Mechanistic insights uncover novel key early and intermediate stages of condensation that can be targeted for p53 rescuing drug discovery.