Convergence of TCDD Gene Activation with Other Pathways

描述(由申请人提供)：本计划的长期目标是 剖析环境污染物的分子机制(S)， 主要是2，3，7，8，四氯二苯并对二恶英(TCDD)，起肿瘤作用 推动者。TCDD的许多不良生物效应被认为是发生的 在激活芳香烃受体(AHR)后，二聚化 AHR与其DNA结合伙伴芳香烃受体核的关系 转位蛋白(ArnT)和AHR/Arnt异源二聚体激活基因。在这里，我们 暗示存在一种额外的机制；TCDD诱导核 AHR的定位及其与ARNT的异二聚化破坏ARNT 从它在其他信号通路中的作用，即Myc/Max的作用 杂二聚体。MYC/MAX是一种众所周知的细胞增殖调节因子， 部分通过基因上调而起作用的细胞凋亡和分化 比如P53。我们发现10Arnt协同作用增强了Myc的能力 上调P53启动子，2)Arnt对Myc的协同作用 反式激活是通过ARNT的HLH域发生的，3)TCDD降低了mRNA P53水平和Myo上调P53启动子的能力。这些 结果，以及其他人的结果，构成了我们假设阿尔特采取行动的基础 与Myc/Max异源二聚体协同上调表达 P53的水平。此外，我们假设TCDD和TCDD的添加 Arnt与AHR的异二聚化，消除了Arnt的这一作用，降低了 Myc调节P53表达水平的能力因此降低 Myc诱导细胞凋亡和分化的能力。为了测试这一想法， 我们将确定ARNT的表达水平是否显著改变 影响Myc上调P53的能力(Aim 1)，促进细胞凋亡 在TCDD存在或不存在的情况下诱导分化(目标2)(目标3)。 然后我们将确定Arnt是否存在于DNA结合复合体中 P53启动子(Aim 4)，并鉴定与Arnt相互作用的蛋白(S)以 诱导其对Myc反式激活的协同作用(目标5)。

DESCRIPTION (provided by applicant): The long-term goals of this proposal are to dissect the molecular mechanism(s) by which environmental contaminants, primarily 2, 3, 7, 8, tetrachlorodibenzo-p-dioxin (TCDD), act as tumor promoters. Many of the adverse biological effects of TCDD are thought to occur following its activation of the aryl hydrocarbon receptor (AHR), dimerization of the AHR with its DNA binding partner, the aryl hydrocarbon receptor nuclear translocator (ARNT) and gene activation by the AHR/ARNT heterodimer. Here, we suggest the existence of an additional mechanism; that TCDD induces nuclear localization of the AHR and its heterodimerization with ARNT that disrupts ARNT from its role in other signaling pathways, i.e., that of the Myc/Max heterodimer. Myc/Max is a well-described regulator of cell proliferation, apoptosis, and differentiation that acts, in part, by upregulation of genes such as p53. We found that 10 ARNT synergistically enhances the ability of Myc to upregulate the p53 promoter, 2) the synergistic actions of ARNT on Myc transactivation occurs via the HLH domain of ARNT, 3) TCDD decreases the mRNA levels of p53 and the ability of Myo to upregulated the p53 promoter. These results, and that of others, form the basis of our hypothesis that ARNT acts synergistically with the Myc/Max heterodimer to upregulate the expression levels of p53. Further, we hypothesize that the addition of TCDD and heterodimerization of ARNT with AHR, removes ARNT form this role, decreases the ability of Myc to regulate the expression levels of p53 and hence, decreases the ability of Myc to induce apoptosis and differentiation. To test this idea, we will determine whether altered expression levels of ARNT significantly impact the ability of Myc to upregulate p53 (Aim 1), and potentiate apoptosis and induce differentiation (Aim 2) in the presence or absence of TCDD (Aim 3). We will then determine whether ARNT is present within DNA binding complexes at the p53 promoter (Aim 4) and identify the protein(s) that interact with ARNT to elicit its synergistic effect on Myc transactivation (Aim 5).