Experimental kinetic mechanism of P53 condensation-amyloid aggregation

Abstract

The tumor suppressor p53 modulates the transcription of a variety of genes constituting a protective barrier against anomalous cellular proliferation. High frequency "hot-spot" 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 sub-micromolar 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 HPV 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 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.