부산대학교 도서관

The p53 tumour suppressor protein is a transcriptional activator, which can induce cell cycle arrest and apoptosis. p53 Gene mutations occur in more than 50% of all human tumours. Reintroduction of wild-type p53 but also of oligomerisation-independent p53 variants into tumour cells by gene transfer methods has been considered. We have investigated the biological properties of two carboxy-terminal deletion mutants of p53, p53Δ300 (comprising amino acids 1–300) and p53Δ326 (amino acids 1–326), to evaluate their potential deployment in gene therapy. Transactivation was measured in transiently transfected HeLa and SKBR3 cells. Both monomeric variants showed reduced activities compared with wild-type p53. Individual promoters were differently affected. In contrast to wild-type p53, monomeric variants were not able to induce apoptosis. We also provided wild-type p53 and p53Δ326 with tetracycline-regulated promoters and stably introduced these constructs into Saos2 and SKBR3 cells. Upon induction, wild-type p53 expressing cells, but not p53Δ326 expressing cells underwent apoptosis. Consistently, only wild-type p53 expressing cells accumulated p21/waf1/cip1 mRNA and protein and showed increased bax, Gadd45 and mdm2 mRNA. Neither wild-type p53 nor p53Δ326 repressed the transcription of the IGF-1R gene in these cell lines. We conclude that the transactivation potential of monomeric, carboxy-terminally truncated p53 is not sufficient to cause induction of the endogenous target genes which trigger apoptosis. [ABSTRACT FROM AUTHOR]