Upregulation of ITM2A by p53 activation modulates p53 function through physical interaction.

The tumor suppressor p53 plays a crucial role in preventing cancer development, and its dysfunction is frequently observed in various cancers. This study identifies a novel regulatory interaction between p53 and ITM2A. We found that p53 upregulates ITM2A expression, while ITM2A in turn inhibits p53 function, suggesting a negative feedback loop. ITM2A mRNA levels were reduced across multiple tumor types, particularly in those harboring mutant p53, and low ITM2A expression correlated with poor patient survival. Mechanistically, ITM2A physically interacts with p53, selectively modulates its phosphorylation (reducing Ser392 while enhancing Ser37), and promotes cytoplasmic accumulation of p53. These modifications collectively suppress p53-dependent transcription, an effect consistently observed across multiple cell lines under both basal conditions and upon physiological p53 activation by genotoxic stress. Conversely, ITM2A depletion enhances p53 nuclear accumulation and transcriptional activity. These findings reveal a novel autoregulatory circuit wherein p53 induces ITM2A expression, which then attenuates p53 activity, suggesting ITM2A as a potential prognostic marker and therapeutic target for cancers with dysregulated p53 signaling.