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Title: The destabilising effects of tumorigenic p53 mutations
Author: Bullock, A. N.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2000
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The tumour suppressor p53 is mutated in half of all human cancers, most frequently with missense substitutions in its core domain. The two most frequent mutations remove DNA-binding interactions, but the majority of mutations destabilise the core domain structure. I have established an assay for the thermodynamic stability of the core domain using reversible urea-induced denaturation. A systematic study of 19 mutants provides several insights into the properties of tumorigenic p53 mutations. Firstly, five mutant classes are identified that correlate with four well-defined regions of the core domain structure. This simple pattern forms the basis for a quantitative understanding of the 10 000 cancer entries in the IARC p53 mutation database. Secondly, a thermodynamic stability threshold (ΔΔGH2O D-N ≥ 3.0 kcal/mol) is identified, beyond which all core domain mutations are expected to promote cancer. In agreement with previous stability studies on model proteins, these are largely restricted to the protein's hydrophobic core and involve the same empirical rules for the loss of methyl(ene) groups or hydrogen bond partners. Extrapolation to the physiological state shows that the wild-type domain has a stability of 3.0 kcal/mol, so these mutants are at least 50 % denatured. Thirdly, a small molecule is used to restore wild-type stability to the hotspot mutant G245S, proving in principle that drug rescue of mutant p53 is a viable therapeutic strategy to aid future anti-cancer regimes. Finally, a peptide selected by phage display suggests a mechanism by which the mutated core domain abrogates the function of the N-terminal transactivation domain. These studies provide a set of reference data to interpret in vivo studies and to further the development of future therapeutic strategies.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available