ポスターセッション

一覧　トップ

TNFαは変異型p53に対し、p21プロモーター結合能を誘導するが、転写活性は誘導しない。：¹小林信義、高田康成、蜂谷みさを、大沢宜明、²中島伸之、明石真言 (放医研・放射線障害医療部、千葉大・医・一外²）

TNFα induces the DNA-binding capacity of mutant p53 but fails to transactivate the p21 promoter in colon cancer cells WiDr. : ¹Nobuyoshi KOBAYASHI, ¹Yasunari TAKADA, ¹Misao HACHIYA, ¹Yoshiaki OHSAWA, ²Nobuyuki NAKAJIMA, ¹Makoto AKASHI (¹Natl. Inst. Radiol. Sci., ²1st Dept. Surg. Chiba Univ.)

Cell cycle progression in mammalian cells is controlled by the ordered activation of cyclin/cyclin-dependent kinase (CDK) complexes. The p21, a CDK inhibitor, is a key factor in such events and the expression is regulated by the functional p53 tumor suppressor. Previously, we showed that tumor necrosis factor a (TNFα) induced p21 expression in colon cancer cells WiDr with mutated p53 at codon 273 (Histidine replacing Arginine, His273). In order to study the role of the p53 in p21 expression by TNFα, gel electrophoretic mobility shift assays were carried out with oligonucleotide containing the p21 p53-binding site. TNFa induced the DNA-binding capacity of nuclear extracts from cells; a visible DNA-protein complex was detected at 10 min after exposure to TNFα and the binding activity peaked at 60 min. The complex was competed with excess unlabeled oligonucleotide. Furthermore, we studied transactivational properties of the p53 His273. Co-transfection of the p53 His273 expression construct with a luciferase gene controlled by the p21 promoter in cells lacking p53 showed that the p53 His273 was inactive in transactivation while wild-type p53 had strong transactivity. Our results indicate that TNFα induces the DNA-binding capacity of the p53 His273 but fails to transactivate the p21 promoter. We conclude the induction of p21 by TNFa occurs independent of p53 in WiDr cells.