Background: The intrinsically disordered N-ter domain (NTD) of p53 encompasses approximately hundred amino acids that contain a transactivation domain (1-73) and a proline-rich domain (64-92) and is responsible for transactivation function and apoptosis. It also possesses an auto-inhibitory function as its removal results in remarkable reduction in dissociation of p53 from DNA. Principal Findings/Methodology: In this report, we have discovered that p53-NTD spanning amino acid residues 1-125 (NTD125) interacted with WT p53 and stabilized its wild type conformation under physiological and elevated temperatures, both in vitro and in cellular systems. NTD125 prevented irreversible thermal aggregation of heat denatured p53, enhanced p21-5′-DBS binding and further restored DBS binding activity of heat-denatured p53, in vitro, in a dose-dependent manner. In vivo ELISA and immunoprecipitation analysis of NTD125-transfected cells revealed that NTD125 shifted equilibrium from p53 mutant to wild type under heat stress conditions. Further, NTD125 initiated nuclear translocation of cytoplasmic p53 in transcriptionally active state in order to activate p53 downstream genes such as p21, Bax, PUMA, Noxa and SUMO. Conclusion/Significance: Here, we showed that a novel chaperone-like activity resides in p53-N-ter region. This study might have significance in understanding the role of p53-NTD in p53 stabilization, conformational activation and apoptosis under heat-stress conditions.
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