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 "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. SIGNIFICANT STATEMENTKnown as "the guardian of the genome", the tumor suppressor protein p53 becomes activated by injuries to the DNA genome, and determines whether the cell must undergo self-destruction to avoid cancerous proliferation. P53 is in fact inactivated by mutations in over 50% of all cancers, and restoring its function is recognized as a therapeutic cancer target. A recent biochemical revolution in cell physiology and pathology are liquid entities known as biomolecular condensates. We show that p53 form condensates en route to pathological forms in a surprisingly similar manner to neurological amyloid diseases such as Alzheime[r]s and Parkinso[n]s. We uncover the sequence of steps in the reaction, exposing flanks for a novel drug development platform based on the condensates paradigm.