Human p53-p51 (p53-related) fusion protein: A potent BAX transactivator

We recently discovered human p51, a new gene structurally and functionally related to human p53, This gene encodes two major splicing variants, p51A a nd p51B, which differ in their carboxy-terminal structure. However, p51A sh ows strong transactivation potential, while p51B has only weak potential. T o clarify the reason for this difference, we made chimeric gene constructs expressing fusion proteins of p53-p51A and p53-p51B, having an N-terminus o f p53 and a C-terminus of p51A. or p51B, respectively, In a BAX promoter-lu ciferase assay using p53-deficient SAOS-2 cells, they exhibited up to 30-fo ld stronger transactivation potential than p53 and p51A themselves, suggest ing that the C-terminus of p51B does not simply serve as a repressor We obt ained similar results with p21(WAF1) promoter-reporter plasmids, These chim eras will,be valuable tools for gene therapy.