Pietsch E Christine, Chan Jefferson Y, Torti Frank M, Torti Suzy V
Department of Biochemistry, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA.
J Biol Chem. 2003 Jan 24;278(4):2361-9. doi: 10.1074/jbc.M210664200. Epub 2002 Nov 14.
Ferritin is a ubiquitous intracellular iron storage protein that consists of 24 subunits of the H and L type. The ability to sequester iron from participation in oxygen free radical formation is consistent with a cytoprotective role for ferritin. Here we demonstrate that ferritins H and L are induced in cells treated with beta-napthoflavone (beta-NF) and chemopreventive dithiolethiones. Induction of ferritin H by beta-NF and the dithiolethiones oltipraz and 1,2-dithiole-3-thione (D3T) occurs via a transcriptional mechanism that is mediated by the ferritin H electrophile/antioxidant-responsive element (EpRE/ARE). The murine ferritin H gene contains five potential xenobiotic-responsive element (XRE) sequences in its 5'-promoter region. However, deletion analysis demonstrates that these XRE sequences are not functional in inducing ferritin H in response to beta-NF. Electrophoretic mobility shift assays demonstrate that the ferritin H EpRE/ARE binds Nrf2. Transfection of chimeric ferritin H reporter genes with Nrf2 expression vectors and Nrf2 dominant-negative mutants indicate that Nrf2 functions at the EpRE/ARE to mediate transcriptional activation of ferritin H. Induction of ferritin H and L was not seen in Nrf2 knockout cells, demonstrating that this transcription factor is required for the induction of ferritin in response to polycyclic aromatic xenobiotics and chemopreventive agents. Nrf2 may also play a role in basal transcription of both ferritin H and L. These results provide a mechanistic link between regulation of the iron storage protein ferritin and the cancer chemopreventive response.
铁蛋白是一种普遍存在的细胞内铁储存蛋白，由24个H型和L型亚基组成。其从参与氧自由基形成中螯合铁的能力与铁蛋白的细胞保护作用一致。在此我们证明，在经β-萘黄酮（β-NF）和化学预防剂二硫代硫酮处理的细胞中，铁蛋白H和L会被诱导。β-NF以及二硫代硫酮奥替普拉和1,2-二硫醇-3-硫酮（D3T）对铁蛋白H的诱导是通过一种转录机制发生的，该机制由铁蛋白H亲电试剂/抗氧化剂反应元件（EpRE/ARE）介导。小鼠铁蛋白H基因在其5'-启动子区域包含五个潜在的外源性物质反应元件（XRE）序列。然而，缺失分析表明这些XRE序列在响应β-NF诱导铁蛋白H时不起作用。电泳迁移率变动分析表明，铁蛋白H的EpRE/ARE与Nrf2结合。用Nrf2表达载体和Nrf2显性负性突变体转染嵌合铁蛋白H报告基因表明，Nrf2在EpRE/ARE处发挥作用，介导铁蛋白H的转录激活。在Nrf2基因敲除细胞中未观察到铁蛋白H和L的诱导，这表明该转录因子是响应多环芳烃外源性物质和化学预防剂诱导铁蛋白所必需的。Nrf2可能也在铁蛋白H和L的基础转录中发挥作用。这些结果为铁储存蛋白铁蛋白的调节与癌症化学预防反应之间提供了一个机制联系。
