Transcriptional Control of Drosophila Detoxification Genes

描述（由申请人提供）：动物的生存受到热休克、氧化应激、缺氧、感染和来自环境的毒性挑战等形式的持续威胁。为了对抗这些威胁并维持体内平衡，动物进化出了复杂而特定的调控反应，其中包括关键防御基因的协调转录控制。许多这些调节网络已经在果蝇果蝇中被识别和表征，并通过进化被证明是保守的，为理解它们在人类中的控制提供了基础。这些反应也为高等生物协调转录控制的分子机制提供了关键的见解。值得注意的是，动物最关键的防御反应之一——对有害化学物质的解毒能力——还没有用一个简单的遗传模型系统来描述。这些化合物包括药品、农药、植物毒素和污染物，统称为外源性物质，是癌症和呼吸系统疾病的一个重要危险因素。异种反应也仍然是制药业开发新药的主要障碍。我们已经证明，用一种广泛使用的外源药物，镇静剂苯巴比妥治疗果蝇，会导致基因表达的快速、广泛和协调的变化。许多苯巴比妥调节的基因编码酶，并提出了与解毒、保护、药物运输或排泄一致的功能。DHR96（脊椎动物外源受体PXR和CAR的单一祖先苍蝇同源物）的零突变影响其中一些基因的苯巴比妥调节，表明DHR96可以像其脊椎动物对应物一样通过促进昆虫的外源反应发挥作用。然而，在缺乏DHR96的情况下，大多数基因都可以通过药物进行适当的调节，在小鼠PXR和CAR突变体中也可以看到这种效果，这就提出了如何控制这种协调转录回路的问题。本提案的目的是利用果蝇来定义异种生物转录反应的分子机制。我们将确定苯巴比妥调节所需的关键启动子序列

DESCRIPTION (provided by applicant): Animals live with constant threats to their survival in the form of heat shock, oxidative stress, hypoxia, infection, and toxic challenges from the environment. To combat these threats and maintain homeostasis, animals have evolved complex and specific regulatory responses that include the coordinated transcriptional control of key defensive genes. Many of these regulatory networks have been identified and characterized in the fruit fly Drosophila melanogaster, and shown to be conserved through evolution, providing a foundation for understanding their control in humans. These responses have also provided key insights into the molecular mechanisms of coordinate transcriptional control in higher organisms. Remarkably, one of the most critical defense responses in animals - the ability to detoxify harmful chemicals - has not yet been characterized using a simple genetic model system. These compounds, which include pharmaceuticals, pesticides, plant toxins, and pollutants, referred to collectively as xenobiotics, comprise a critical risk factor for cancer and respiratory diseases. Xenobiotic responses also remain a major impediment to the development of new drugs by the pharmaceutical industry. We have shown that treatment of Drosophila with a widely used xenobiotic, the sedative phenobarbital, results in a rapid, widespread, and coordinate change in gene expression. Many phenobarbital-regulated genes encode enzymes and have proposed functions consistent with detoxification, protection, drug transport, or excretion. A null mutation in DHR96 - the single ancestral fly ortholog of the vertebrate xenobiotic receptors PXR and CAR - affects the phenobarbital regulation of some of these genes, demonstrating that DHR96 can function like its vertebrate counterparts by contributing to xenobiotic responses in insects. Most genes, however, are properly regulated by drug in the absence of DHR96, an effect also seen in mouse PXR and CAR mutants, raising the question of how this coordinate transcriptional circuit is controlled. The goal of this proposal is to use Drosophila to define the molecular mechanisms of xenobiotic transcriptional responses. We will identify critical promoter sequences that are required for phenobarbitalregulated transcription and characterize the trans-acting factors that confer this control. We will also determine the molecular mechanisms by which DHR96 contributes to xenobiotic transcriptional responses. This research will provide new insights into how higher organisms, including humans, cope with toxic compounds in their environment and establish Drosophila as a new model system for characterizing xenobiotic response regulation.