p53 Amino-Terminus Region (1–125) Stabilizes and Restores Heat Denatured p53 Wild Phenotype

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

The structure of p53 tumour suppressor protein reveals the basis for its funcitonal plasticity

p53 major tumour suppressor protein has presented a challenge for structural biology for two decades. The intact and complete p53 molecule has eluded previous attempts to obtain its structure, largely due to the intrinsic flexibility of the protein. Using ATP-stabilised p53, we have employed cryoelectron microscopy and single particle analysis to solve the first three-dimensional structure of the full-length p53 tetramer (resolution 13.7 Å). The p53 molecule is a D2 tetramer, resembling a hollow skewed cube with node-like vertices of two sizes. Four larger nodes accommodate central core domains, as was demonstrated by fitting of its X-ray structure. The p53 monomers are connected via their juxtaposed N- and C-termini within smaller N/C nodes to form dimers. The dimers form tetramers through the contacts between core nodes and N/C nodes. This structure revolutionises existing concepts of p53's molecular organisation and resolves conflicting data relating to its biochemical properties. This architecture of p53 in toto suggests novel mechanisms for structural plasticity, which enables the protein to bind variably spaced DNA target sequences, essential for p53 transactivation and tumour suppressor functions