GAIN OF FUNCTION PHENOTYPE OF TUMOR-DERIVED MUTANT P53 REQUIRES THE OLIGOMERIZATION NONSEQUENCE-SPECIFIC NUCLEIC ACID-BINDING DOMAIN/

Tumor-derived p53 mutants can transcriptionally activate a number of p romoters of genes involved in cellular proliferation. For this transac tivation, mutant p53 does not use the wild-type p53 DNA-binding site, suggesting a mechanism of transactivation that is independent of direc t DNA binding. Here me describe our analysis of the domain requirement s for mutant p53 to transactivate promoters of the human epidermal gro wth factor receptor (EGFR), human multiple drug resistance 1 (MDR-1) a nd human proliferating cell nuclear antigen (PCNA) genes. We also repo rt the identification of a structural domain required for the 'Gain of function' property of mutant p53-281G, 'Gain of function' is measured as the tumorigenicity (in nude mice) of 10(3) murine cells expressing mutant p53 constitutively. We have generated internal deletion mutant s of p53-281G deleting conserved domains I, II, III, IV and V, individ ually. We have also generated one deletion mutant eliminating amino ac ids 100 through 300 that removes four of the five conserved domains (I I-V); another mutant, p53-281G del 393-327, deletes the oligomerizatio n and nonsequence-specific nucleic acid-binding domains of p53, For th e EGFR and MDR-1 promoters, all these mutants have significantly lower transactivation ability than intact p53-281G, These deletion mutants, however, significantly activated the pCNA promoter, suggesting that t he mechanism of transactivation of the PCNA promoter is different from that of the EGFR and MDR-I promoters, When expressed constitutively i n 10(3) cells, p53-281G del 393-327 was found to be defective in induc ing tumor formation in nude mice although intact p53-281G was very eff icient. Thus, our results suggest that structural domains near the C-t erminus are needed for 'gain of function'.