Scientists discovered that the anti‑aging peptide FOXO4‑DRI sticks to a part of the p53 protein that’s usually floppy, and this binding helps kill old, senescent cells. The peptide works best when p53 is phosphorylated, and the study maps out exactly how the two molecules fit together.

A central process contributing to the phenotype of aging is cellular senescence. We recently identified the FOXO4 - p53 axis as pivotal in maintaining the viability of senescent cells, and that senescent cells can be targeted selectively with the senolytic peptide FOXO4-DRI. Here, we solve the solution NMR structural models of the p53 transactivation domain in complex with the FOXO4 forkhead domain and in complex with FOXO4-DRI. Strikingly, we find that the disordered FOXO4-DRI binds to the disordered p53^TAD2 and forms a transiently folded complex. In this complex, both, the FOXO4-derived region and the cationic cell permeability peptide contribute to the interaction. Furthermore, we show that p53 phosphorylation enhances the affinity for both FOXO4 and FOXO4-DRI. Summarizing we provide a detailed characterization of the interaction of p53 with FOXO4 and FOXO4-DRI which is the basis for development of p53 inhibitors to treat diseases linked to cellular senescence such as cancers.