The characterisation of p53 binding phage isolated from phage peptide display libraries

Peptide phage display libraries were screened for peptides that bind to the tumour suppressor protein, human p53. Three p53 binding peptides were isolated respectively from hexamer (6-mer), dodecamer (12-mer) and icosomer (20-mer) libraries. We have characterised their interaction with p53 in detail. The phage appear to bind regions on native p53 common between mouse and man. Two conformation-specific anti-p53 monoclonal antibodies were used to dissect the phage-p53 interaction, the phage were found to preferentially bind the PAb1620-p53 conformation rather than the PAb240-p53 conformation. Mapping experiments indicated the C-terminal 30 amino acid residues of p53 were dispensable for phage binding and that the binding of SV40 large T-antigen and the phage were not mutually exclusive. Interestingly the phage were seen to exhibit differential binding to wild-type human p53 over the two point mutant p53 proteins, His175 and Trp248. Ultimately the phage appear to selectively target native wild-type p53, mimicking the specificity of SV40 large T-antigen. The ability to target specific sub-populations of p53 could be an important step in the development of therapeutics for the treatment of p53-based human malignancy.