肿瘤坏死因子-α在p53基因发生突变的结肠癌细胞WiDr中诱导p21（WAF1）表达，但不诱导Bax表达：蛋白质稳定化的重要作用

TNF-alpha induced p21(WAF1) but not Bax in colon cancer cells WiDr with mutated p53: important role of protein stabilization.

作者信息

Kobayashi N, Takada Y, Hachiya M, Ando K, Nakajima N, Akashi M

机构信息

Division of Radiation Health, National Institute of Radiological Sciences, Chiba 263-8555, Japan.

出版信息

Cytokine. 2000 Dec;12(12):1745-54. doi: 10.1006/cyto.2000.0782.

DOI:10.1006/cyto.2000.0782

PMID:11097743

Abstract

The p21(WAF1)induces cell cycle arrest at G(1)and its expression is regulated by the functional p53. TNF-alpha induced expression of p21(WAF1)at protein and mRNA levels in a dose-dependent fashion with an association with G(1)-arrest in human colon cancer cells WiDr that carry mutated p53 at codon 273 (His(273)). However, TNF-alpha did not affect the levels of the Bax protein, which also has p53-binding sites on its promoter and causes apoptosis. Further experiments suggested that cycloheximide (CHX), a protein synthesis inhibitor, increased the levels of p21(WAF1)mRNA and the induction of p21(WAF1)mRNA by TNF-alpha did not require new protein synthesis. Co-transfection of the p53 His(273)expression construct with a luciferase gene controlled by the p21(WAF1)promoter showed that the p53 His(273)was inactive, although TNF-alpha increased the transcriptional rate of p21(WAF1)in these cells. Further study found that TNF-alpha markedly stabilized the p21(WAF1)protein. These findings suggest that TNF-alpha induces expression of p21(WAF1)through a distinct pathway from Bax and that protein stabilization is an important mechanism in the expression of p21(WAF1)independent of p53.

摘要

p21（WAF1）可诱导细胞周期在G1期停滞，其表达受功能性p53调控。肿瘤坏死因子-α（TNF-α）在携带密码子273（His(273)）处p53突变的人结肠癌细胞WiDr中，以剂量依赖方式诱导p21（WAF1）在蛋白和mRNA水平的表达，并与G1期停滞相关。然而，TNF-α并未影响Bax蛋白水平，Bax蛋白在其启动子上也有p53结合位点并可导致细胞凋亡。进一步实验表明，蛋白质合成抑制剂放线菌酮（CHX）可增加p21（WAF1）mRNA水平，且TNF-α诱导p21（WAF1）mRNA表达不需要新的蛋白质合成。将p53 His(273)表达构建体与受p21（WAF1）启动子控制的荧光素酶基因共转染显示，尽管TNF-α增加了这些细胞中p21（WAF1）的转录速率，但p53 His(273)无活性。进一步研究发现，TNF-α可显著稳定p21（WAF1）蛋白。这些发现表明，TNF-α通过与Bax不同的途径诱导p21（WAF1）表达，且蛋白质稳定化是p21（WAF1）表达中独立于p53的重要机制。