Single-chain antibody against the common epitope of mutant p53: isolation and intracytosolic expression in mammalian cells

Abstract

The peptide epitope FRHSVV is cryptic in wild-type p53 and is exposed in many types of mutant p53 molecules isolated from various tumors. Mutant p53 marked by this epitope abrogates a tumor-suppressor function of wild-type p53 and possibly contributes to the transforming potential of other oncogenic processes. We report here the construction of a single-chain scFv antibody gene library derived from the mRNA of a mouse immunized with the epitope peptide FRHSVV which mimics the common epitope in p53 mutant protein molecules. The scFv was presented by phage display. The selected antibody gene, named ME1, was found to bind to the mutant p53 protein but not to the wild-type p53 protein. Preliminary studies show that the ME1 gene is expressed in the cytosol of mammalian cells. These findings suggest that the ME1 single-chain antibody may be useful as a tool for clarifying the role of mutant p53 in tumor transformation, especially in cells heterozygous in p53, and possibly for gene therapy of tumors.