Denison M S, Deal R M
Department of Biochemistry, Michigan State University, East Lansing 48823.
Mol Cell Endocrinol. 1990 Feb 12;69(1):51-7. doi: 10.1016/0303-7207(90)90088-p.
The biological effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, dioxin), a potent environmental contaminant, are mediated by a soluble intracellular protein, the aromatic hydrocarbon (Ah) receptor (AhR). TCDD:AhR complexes activate gene transcription by binding to specific DNA sequences termed dioxin-responsive elements adjacent to TCDD-responsive genes. Analogies between the AhR and receptors for steroid hormones imply similarities in their mechanism of action. The presence of chelatable, protein-bound metal(s), presumably zinc, is required for DNA binding of several proteins, including steroid hormone receptors and the transcription factor SP1. Utilizing gel retardation and DNA-cellulose binding assays we have investigated the importance of metal in DNA binding of transformed TCDD:AhR complexes. Here, we report that although 1,10-phenanthroline, a metal ion chelating agent, inhibited the DNA binding of SP1 and transformed glucocorticoid receptor, no inhibition of transformed AhR was observed. EDTA was similarly ineffective in inhibiting DNA binding of transformed AhR. Our findings suggest that the AhR, although similar to steroid receptors, appears not to require metals for binding to its specific DNA recognition sequence.
2,3,7,8 - 四氯二苯并 - p - 二噁英（TCDD，二噁英）是一种强效环境污染物，其生物学效应由一种可溶性细胞内蛋白质——芳烃（Ah）受体（AhR）介导。TCDD:AhR复合物通过与TCDD反应基因附近的特定DNA序列（称为二噁英反应元件）结合来激活基因转录。AhR与类固醇激素受体之间的相似性暗示了它们作用机制的相似性。包括类固醇激素受体和转录因子SP1在内的几种蛋白质的DNA结合需要存在可螯合的、与蛋白质结合的金属（可能是锌）。利用凝胶阻滞和DNA - 纤维素结合试验，我们研究了金属在转化的TCDD:AhR复合物DNA结合中的重要性。在此，我们报告，尽管金属离子螯合剂1,10 - 菲咯啉抑制了SP1和转化的糖皮质激素受体的DNA结合，但未观察到对转化AhR的抑制作用。EDTA在抑制转化AhR的DNA结合方面同样无效。我们的研究结果表明，AhR虽然与类固醇受体相似，但似乎不需要金属来结合其特定的DNA识别序列。
