Mathieu M C, Lapierre I, Brault K, Raymond M
Institut de Recherches Cliniques de Montréal, Montréal, Québec H2W 1R7, Canada.
J Biol Chem. 2001 Feb 16;276(7):4819-27. doi: 10.1074/jbc.M008495200. Epub 2000 Nov 28.
The mouse multidrug resistance gene family consists of three genes (mdr1, mdr2, and mdr3) encoding P-glycoprotein. We show that the expression of mdr1 is increased at the transcriptional level upon treatment of the hepatoma cell line Hepa-1c1c7 with the polycyclic aromatic hydrocarbon 3-methylcholanthrene (3-MC). This increase is not observed in the aromatic hydrocarbon receptor (AhR)-defective TAOc1BP(r)c1 and the AhR nuclear translocator (Arnt)-defective BP(r)c1 variants, demonstrating that the induction of mdr1 by 3-MC requires AhR.Arnt. We show that the mdr1 promoter (-1165 to +84) is able to activate the expression of a reporter gene in response to 3-MC in Hepa-1c1c7 but not in BP(r)c1 cells. Deletion analysis indicated that the region from -245 to -141 contains cis-acting sequences mediating the induction, including a potential p53 binding sequence. 3-MC treatment of the cells increased the levels of p53 and induced p53 binding to the mdr1 promoter in an AhR.Arnt-dependent manner. Mutations in the p53 binding site abrogated induction of mdr1 by 3-MC, indicating that p53 binding to the mdr1 promoter is essential for the induction. Benzo(a)pyrene, a polycyclic aromatic hydrocarbon and AhR ligand, which, like 3-MC, is oxidized by metabolizing enzymes regulated by AhR.Arnt, also activated p53 and induced mdr1 transcription. 2,3,7,8-Tetrachlorodibenzo-p-dioxin, an AhR ligand resistant to metabolic breakdown, had no effect. These results indicate that the transcriptional induction of mdr1 by 3-MC and benzo(a)pyrene is directly mediated by p53 but that the metabolic activation of these compounds into reactive species is necessary to trigger p53 activation. The ability of the anticancer drug and potent genotoxic agent daunorubicin to induce mdr1 independently of AhR.Arnt further supports the proposition that mdr1 is transcriptionally up-regulated by p53 in response to DNA damage.
小鼠多药耐药基因家族由三个编码P-糖蛋白的基因（mdr1、mdr2和mdr3）组成。我们发现，用多环芳烃3-甲基胆蒽（3-MC）处理肝癌细胞系Hepa-1c1c7后，mdr1的表达在转录水平上增加。在芳烃受体（AhR）缺陷型TAOc1BP(r)c1和AhR核转运蛋白（Arnt）缺陷型BP(r)c1变体中未观察到这种增加，这表明3-MC对mdr1的诱导需要AhR.Arnt。我们发现mdr1启动子（-1165至+84）能够响应3-MC在Hepa-1c1c7中激活报告基因的表达，但在BP(r)c1细胞中则不能。缺失分析表明，-245至-141区域包含介导诱导作用的顺式作用序列，包括一个潜在的p53结合序列。用3-MC处理细胞可增加p53的水平，并以AhR.Arnt依赖的方式诱导p53与mdr1启动子结合。p53结合位点的突变消除了3-MC对mdr1的诱导作用，表明p53与mdr1启动子的结合对于诱导作用至关重要。苯并(a)芘是一种多环芳烃和AhR配体，与3-MC一样，可被AhR.Arnt调节的代谢酶氧化，它也能激活p53并诱导mdr1转录。2,3,7,8-四氯二苯并对二恶英是一种抗代谢分解的AhR配体，没有作用。这些结果表明，3-MC和苯并(a)芘对mdr1的转录诱导直接由p53介导，但这些化合物代谢活化为反应性物种是触发p53激活所必需的。抗癌药物和强效基因毒性剂柔红霉素能够独立于AhR.Arnt诱导mdr1，这进一步支持了mdr1在DNA损伤应答中被p53转录上调的观点。
