REGULATION OF IRON HOMEOSTASIS IN OXIDATIVE STRESS

描述（由申请方提供）：诱导解毒酶是对抗致癌物和化学/氧化应激的重要细胞保护机制。抗氧化解毒基因在氧化应激中的转录激活是由一个顺式作用元件（antioxidant response element，ARE）驱动的，然而ARE增强子在氧化应激中被激活的分子机制尚未完全阐明。铁蛋白由24个H和L型亚基组成，是一种普遍存在且高度保守的铁储存蛋白，在维持铁稳态中起着重要作用。铁蛋白对细胞内游离铁的螯合是一种重要的细胞防御机制，因为它限制了铁催化产生的羟基自由基，从而引起氧化应激和细胞损伤。事实上，其他人和我们证明，氧化应激激活铁蛋白H和L基因的转录。然而，铁蛋白转录被氧化应激激活的分子机制仍然未被探索。这项研究的总体目标是了解铁蛋白H基因在氧化应激反应中转录激活的分子机制。我们建议，氧化应激激活特定的转录因子的翻译后修饰，然后结合到75 bp的氧化应激反应元件（OSRE）组成的两个双向ARE图案的铁蛋白H基因。此外，取决于细胞的氧化条件，铁蛋白HOSRE中的两个ARE基序可以充当双链和单链（茎环）DNA增强子元件。为了验证这一假设，我们将：1）鉴定与OSRE结合并响应氧化应激激活铁蛋白H基因转录的转录因子和衔接蛋白，和2）阐明氧化应激-介导的转录因子和信号通路的翻译后修饰，导致铁蛋白H基因的转录激活。这些研究将为我们了解铁蛋白H基因的分子生物学机制提供重要信息。铁蛋白H基因的转录通过ARE基序响应于氧化应激而被激活，并且最终通过铁稳态被调节以在促氧化剂条件下使氧化细胞损伤最小化的机制。

DESCRIPTION (provided by applicant): Induction of detoxification enzymes is an important mechanism of cytoprotection against carcinogens and chemical/oxidative stress. Transcriptional activation of antioxidant detoxification genes by oxidative stress is driven by a cis-acting element, termed the antioxidant response element (ARE), however, the molecular mechanisms by which the ARE enhancer is activated by oxidative stress are not fully elucidated.Ferritin, composed of 24 subunits of the H and L types, is a ubiquitous and highly conserved iron-storage protein that plays a prominent role in maintaining iron homeostasis. Sequestration of intracellular free iron by Ferritin is an important cellular defense mechanism because it limits iron-catalyzed generation of hydroxyl radicals that elicit oxidative stress and cell damage. Indeed, others and we demonstrated that oxidative stress activates transcription of the ferritin H and L genes. However, the molecular mechanisms by which ferritin transcription is activated by oxidative stress remain unexplored. The overall goal of this research proposal is to understand molecular mechanisms underlying transcriptional activation of the ferritin H gene in response to oxidative stress. We propose that oxidative stress activates specific transcription factors by posttranslational modifications, which then bind to the 75 bp oxidative stress response element (OSRE) composed of two bidirectional ARE motifs in the ferritin H gene. Moreover, depending on oxidative conditions of the cells, the two ARE motifs in the ferritin H OSRE may function as both double strand and single strand (stem loop) DNA enhancer elements. To test this hypothesis we will, 1) identify the transcription factors and adaptor proteins that bind to the OSRE and activate transcription of the ferritin H gene in response to oxidative stress, and 2) elucidate oxidative stress-mediated posttranslational modifications of transcription factors and signaling pathways leading to transcriptional activation of the ferritin H gene.These studies will provide significant information for our understanding of molecular mechanisms by which transcription of the ferritin H gene is activated via ARE motifs in response to oxidative stress, and ultimately by which iron homeostasis is tuned to minimize oxidative cell damage under prooxidant conditions.