Analysis of human p53 proteins and mRNA levels in normal and transformed cells

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Abstract
P53 mRNA and proteins were examined in a variety of human transformed cells and in normal human foreskin fibroblast cells. Both the steady‐state and translatable levels of p53 mRNA were the same in normal and transformed human cells. In vitro synthesized p53, programmed by mRNA from normal and transformed human cells, revealed that there was heterogeneity in the primary structure of p53 from these cells. Pulse labeling of cells and immunoprecipitation analysis with a panel of human reactive anti‐p53 antibodies demonstrated that the types of p53 synthesized in vitro corresponded to the types made in vivo from SV80 and COLO 320 cells. No p53 was detectable by similar pulse‐labeling analysis of HeLa and normal foreskin fibroblast cells. Since it was necessary to use anti‐p53 sera from cancer patients to carry out much of the immunoprecipitation analysis in this study we therefore further characterised these sera to determine if they reacted with one or more than one epitope. p53‐β‐galactosidase fusion proteins were synthesized in Escherichia coli and used to analyse the anti‐p53 antibodies produced by cancer patients. We demonstrate that the antisera contain antibodies directed against epitopes in both the N‐terminal and C‐terminal regions of the p53 molecule.