Mutant p53 R273H disrupts PDPK1 homodimerization and contributes to PDPK1 activation

The tumor suppressor p53 protein is frequently mutated in cancer, conferring oncogenic gain‐of‐function properties. One such mutant, p53 R273H , is known to promote the activation of the PI3K/AKT pathway, but the underlying mechanism is unclear. Here, we demonstrated a direct interaction between p53 R273H and 3‐phosphoinositide‐dependent protein kinase 1 (PDPK1), an upstream kinase of AKT. Interestingly, this interaction was unique to p53 R273H , as it was not seen with wild‐type p53 or other hotspot mutants such as p53 R175H and p53 R248W . Mechanistically, our in silico analysis revealed that the R273H mutation exposed a hydrophobic region within the p53 R273H DNA‐binding domain (DBD), facilitating PDPK1 binding. This binding disrupted PDPK1 homodimerization, a known inhibitory mechanism of PDPK1 activity. In contrast, the PDPK1‐binding deficient mutant p53 F270A/R273H did not disrupt PDPK1 homodimerization. We propose that p53 R273H promotes AKT phosphorylation, potentially by enhancing PDPK1 homodimer dissociation. Supporting this, the small molecule PRIMA‐1 Met disrupted the p53 R273H ‐PDPK1 interaction, resulting in reduced AKT phosphorylation. These findings highlight a new gain‐of‐function role of p53 R273H , suggesting that targeting the p53 R273H ‐PDPK1 interaction with PRIMA‐1 Met could dampen AKT phosphorylation in p53 R273H ‐expressing cancers.