title: Factors governing loss and rescue of DNA binding upon single and double mutations in the p53 core domain.
abstract: The mutation of R273-->H in the p53 core domain (p53-CD) is one of the most common mutations found in human cancers. Although the 273H p53-CD retains the wild-type conformation and stability, it lacks sequence-specific DNA binding, a transactivation function and growth suppression. However, mutating T284-->R in the 273H p53-CD restores the DNA binding affinity, and transactivation and tumour suppressor functions. Since X-ray/NMR structures of DNA-free or DNA-bound mutant p53-CD molecules are unavailable, the factors governing the loss and rescue of sequence-specific DNA binding in the 273H and 273H+284R p53-CD, respectively, are unclear. Hence, we have carried out molecular dynamics (MD) simulations of the wild-type, single mutant and double mutant p53-CD, free and DNA bound, in the presence of explicit water molecules. Based on the MD structures, the DNA-binding free energy of each p53 molecule has been computed and decomposed into component energies and contributions from the interface residues. The wild-type and mutant p53-CD MD structures were found to be consistent with the antibody-binding, X-ray and NMR data. The predicted DNA binding affinity and specificity of both mutant p53-CDs were also in accord with experimental data. The non-detectable DNA binding of the 273H p53-CD is due mainly to the disruption of a hydrogen-bonding network involving R273, D281 and R280, leading to a loss of major groove binding by R280 and K120. The restoration of DNA binding affinity and specificity of the 273H+284R p53-CD is due mainly to the introduction of another DNA-binding site at position 284, leading to a recovery of major groove binding by R280 and K120. The important role of water molecules and the DNA major groove conformation as well as implications for structure-based linker rescue of the 273H p53-CD DNA-binding affinity are discussed.
authors.affiliation: Institute of Biomedical Sciences, Academia Sinica, 11529 Taipei, Taiwan.
authors.forename: Jon D
authors.initials: JD
authors.lastname: Wright
authors.forename: Sergey Yu
authors.initials: SY
authors.lastname: Noskov
authors.forename: Carmay
authors.initials: C
authors.lastname: Lim
mesh_terms: D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D015394:Molecular Structure; D009154:Mutation; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary / Q000235:genetics; D013816:Thermodynamics; D016159:Tumor Suppressor Protein p53 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D016159:Tumor Suppressor Protein p53; D004247:DNA