| Abstract: | p53 is a cellular-encoded transformation-related protein. It is synthesized at elevated levels in tumor cells but has also been detected at low concentrations in several types of nontransformed cells. The p53 of tumor cells is immunogenic and elicits specific antibody production. The antigenic determinants of the p53 protein were studied by specific binding to anti-p53 monoclonal antibodies obtained from the RA3-2C2, PAb122, and PAb421 established hybridoma cell lines, and their conservation was followed in various animal species. We found that whereas mouse p53 efficiently immunoprecipitated with all three anti-p53 monoclonal antibodies, human and rat p53 bound PAb122 and PAb421 but lacked a determinant binding RA3-2C2. The hamster p53 molecule represented a third category, which immunoprecipitated with polyclonal anti-p53 antibodies but failed to bind all three monoclonal antibodies analyzed here. Using these monoclonal antibodies, we detected no variations between p53 found in transformed and p53 found in nontransformed cells, within a given species. The results also showed that RA3-2C2, which recognizes a mouse-specific determinant, binds a site located at a proteolytic digestion fragment of the p53 molecule that differs from that containing PAb122 and PAb421 recognition site(s). p53 is a single protein that can be immunoprecipitated through different antigenic determinants that vary between species. |
