REGULATION OF IRON HOMEOSTASIS IN OXIDATIVE STRESS

描述(申请人提供)：解毒酶的诱导是抵抗致癌物质和化学/氧化应激的重要细胞保护机制。氧化应激对抗氧化剂解毒基因的转录激活是由一个被称为抗氧化反应元件(ARE)的顺式作用元件驱动的，然而，氧化应激激活ARE增强子的分子机制尚不完全清楚。铁蛋白是一种普遍存在的高度保守的储铁蛋白，在维持铁稳态方面发挥着重要作用。铁蛋白对细胞内游离铁的隔离是一种重要的细胞防御机制，因为它限制了铁催化的羟基自由基的产生，从而引发氧化应激和细胞损伤。事实上，其他人和我们证明了氧化应激激活了铁蛋白H和L基因的转录。然而，氧化应激激活铁蛋白转录的分子机制尚不清楚。这项研究的总体目标是了解氧化应激下铁蛋白H基因转录激活的分子机制。我们认为，氧化应激通过翻译后修饰激活特定的转录因子，然后与铁蛋白H基因中由两个双向ARE基序组成的75bp氧化应激反应元件(OSRE)结合。此外，根据细胞的氧化条件，这两个基序在铁蛋白H OSRE中可能同时作为双链和单链(茎环)DNA增强子元件发挥作用。为了验证这一假说，我们将从1)鉴定与OSRE结合并激活铁蛋白H基因转录的转录因子和接头蛋白，以及2)阐明氧化应激介导的转录因子的翻译后修饰和导致铁蛋白H基因转录激活的信号通路。这些研究将为我们理解铁蛋白H基因的转录是如何通过ARE基序激活以响应氧化应激的分子机制提供重要信息，并最终通过哪些铁平衡来调节促氧化条件下细胞的氧化损伤。

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.