Transcriptional regulation of arylhydrocarbon receptor (AhR), Arnt and E2F genes on proliferation process in A549 cells by dioxin and its mechanism.

芳烃受体（Arylhydrocarbon receptor，AhR）是一种配体激活的转录因子，介导2，3，7，8-四氯二苯并对二恶英（TCDD）及其相关化合物的一系列毒理学和生物学效应。AhR是一个含有基本螺旋环螺旋/PAS结构域的转录因子家族。AhR的表达与肺癌的发生发展有关。事实上，我们发现AhR的过表达加速了由人肺泡细胞癌建立的A549细胞的细胞增殖。A549细胞增殖的增加与AhR和AhR核转位蛋白（Arnt）的异二聚体复合物的表达激活E2 F基因表达有关，E2 F基因是一种致癌相关的转录因子。本研究旨在探讨E2 F基因激活与AhR/Arnt复合物表达的关系，并通过体外培养获得AhR、Arnt和E2 F基因表达缺失的细胞株， ...更多信息 A549细胞中的iRNA转染技术。AhR、Arnt和E2 F表达的抑制降低了E2 F依赖的转录活性。为了鉴定负责E2 F依赖性转录活性的AhR和Arnt基因的结构域，将一系列与荧光素酶活性相关的缺失构建体转染到A549细胞中。AhR和Arnt序列的PAS区是激活E2 F转录所必需的。接着，通过使用含有XRE序列作为AhR/Arnt结合区的报告分析，确定E2 F表达对AhR和Arnt转录活性的影响。通过抑制E2 F表达，增加了XRE序列上AhR/Arnt复合物依赖的转录活性。E2 F序列中的Rb蛋白结合区是AhR/Arnt复合物相互作用所必需的。Rb蛋白是一种抑癌因子。此外，我们证明了AhR/Arnt复合物与E2 F蛋白复合使用免疫沉淀法。这些结果表明，AhR/Arnt与E2 F结合序列上的E2 F复合物结合促进了细胞增殖，而XRE序列上的复合物结合则作为基因转录的阻遏物受到影响。少

Arylhydrocarbon receptor (AhR) is a ligand-activated transcription factor that mediates a spectrum of toxicological and bio-logical effects of 2,3,7,8-tetrachlorodiben.zo-p-dioxine (TCDD) and related compounds. AhR is included in a family of basic-helix-loop-helix/PAS domain-containing transcription factors. AhR expression is associated with the development of human lung carcinoma. In fact, we found that the overexpression of AhR accelerated the cell proliferation of A549 cells, established from a human alveolar cell carcinoma. We also demonstrated that the increased cell proliferations in A549 cells were associated with the activation of E2F gene expression, a transcription factor related in carcinogenesis, by the expression of heterodimer complex of AhR and AhR nuclear translocator (Arnt). In this study, we investigated the mechanisms of relationship of E2F gene activation and expression of AhR/Arnt complex.We obtained the deleted cell lines of AhR, Arnt and E2F genes expression by s … More iRNA transfection technique in A549 cells. E2F-dependent transcription activity was decreased by the suppression of AhR, Arnt and E2F expression. To identify the domains of AhR and Arnt genes responsible for E2F-dependent transcription activity, a series of deletion constructs linked the luciferase activity were transfected into A549 cells. The PAS regions of AhR and Arnt sequences were required for the activation of E2F transcription. Next, an effect of E2F expression to the transcription activity of AhR and Arnt was determined by using of reporter assay contained XRE sequences, as AhR/Arnt-binding regions. The AhR/Arnt complex-dependent transcription activity on XRE sequences was increased by the suppression of E2F expression. The Rb protein-binding regions in E2F sequences were required on the interaction of AhR/Arnt complex. Rb protein is a repressive factor of carcinogenesis. Furthermore, we demonstrated that AhR/Arnt complex was complexed with E2F protein using a immuno-precipitation assay. These results suggested that AhR/Arnt and E2F complex binding on E2F-binding sequences was accelerated the cell proliferation, while the complex binding on XRE sequences was affected as a repressor in gene transcription. Less