Abstract
Tumor suppressor protein 53 (p53) is a transcription factor that is deregulated in 50% of cancers. Often termed the guardian of the genome, p53 is responsible for maintenance of genomic stability, cell cycle arrest, DNA repair, senescence, and apoptosis. In cancer cells, deregulation of p53 often occurs through mutations in the DNA binding domain which lead to a loss of the transcriptional activity. While 100's of somatic mutations in the DNA binding domain are known, a small number of mutants are enriched in cancer, suggesting a gain-of-function role. Here we deploy an intein-based approach to localize μMap photoproximity labeling to p53 to define novel interactions contributing to the loss and gain of function roles of 5 separate hotspot mutants. These data revealed that G245S and R273H binds to RNA through its C-terminal domain. We show through CLIP experiments that mutant p53 has an RNA binding motif that conserved across mutants and is enriched in 3'UTRs, promoting ribosomal localization and labeling of proteins at the mitochondrial surface. We further demonstrate that the RNA binding ability of mutant p53 promotes altered miRNA processing and mitochondrial dysfunction providing mechanistic rationale for historically reported but poorly understood phenotypes.