Iron Regulation of Gene Expression

描述（由申请人提供）：铁是许多生物过程所需蛋白质的功能所必需的，包括电子转移，氧运输和DNA合成。铁对生物体是有毒的，因为它能够产生氧化大分子的自由基。过量铁的积累会导致肝硬化、心肌病、糖尿病、神经变性和癌症风险的增加，而缺铁会导致儿童永久性的神经认知和运动障碍。由于铁的有益而有害的作用，哺乳动物细胞已经发展出高度调节的机制来感知、获取和储存铁。我们的目标是确定铁调节蛋白1和2 （IRP1和IRP2）控制铁稳态的机制。IRP1和IRP2结合到铁响应元件（iron-responsive elements, IREs）的mrna编码蛋白中，参与铁的摄取、封存和利用，并调节其翻译和降解。尽管IRP1和IRP2具有相似的序列，但它们对单个mRNA的结合亲和力以及它们的活性受铁调控的机制不同。此外，Irp2-/-小鼠出现神经退行性疾病，而Irp1-/-小鼠未表现出明显异常。我们计划确定IRP1和IRP2的不同作用以及它们调节细胞铁代谢的机制。我们的具体目的是：1)为了确定IRP1和IRP2在铁稳态中的具体作用，我们将研究小鼠IRP2基因内源性编码序列被删除并被IRP1基因所取代的小鼠。我们的目标是利用这些小鼠来确定用IRP1的编码序列替换IRP2的编码序列是否可以挽救IRP2 -/-小鼠的异常，2)确定信号IRP2进行铁介导降解的机制，3)确定IRP2磷酸化的生理意义。

DESCRIPTION (provided by applicant): Iron is required for the function of many proteins that are needed for biological processes, including electron transfer, oxygen transport and DNA synthesis. Iron is toxic to organisms due to its ability to generate free radicals that oxidize macromolecules. The accumulation of excess iron can result in cirrhosis, cardiomyopathy, diabetes mellitus, neurodegeneration, and increased risk of cancer, while iron deficiency can result in permanent neurocognitive and motor impairment in children. Because of the deleterious yet beneficial effects of iron, mammalian cells have developed highly regulated mechanisms to sense, acquire and store iron. Our goal is to determine the mechanisms by which the iron-regulatory proteins 1 and 2 (IRP1 and IRP2) control iron homeostasis. IRP1 and IRP2 bind to iron-responsive elements (IREs) in mRNAs encoding proteins involved in uptake, sequestration and utilization of iron, and regulate their translation and degradation. Although IRP1 and IRP2 have similar sequences, they differ with respect to their binding affinities for individual mRNA's and the mechanism by which their activity is regulated by iron. Furthermore, Irp2-/- mice develop neurodegenerative disease, while Irp1-/- mice display no obvious abnormalities. We plan to determine the distinct roles of IRP1 and IRP2 and the mechanisms by which they regulate cellular iron metabolism. Our specific aims are: 1) to determine specific roles of IRP1 and IRP2 in iron homeostasis, we will study mice in which endogenous coding sequences of the mouse Irp2 gene are deleted and replaced with those of Irp1. Our goal is to use these mice to determine if the replacement of IRP2 coding sequences with those of IRP1 can rescue abnormalities in Irp2-/- mice, 2) to determine the mechanism that signals IRP2 for iron-mediated degradation, and 3) to determine the physiological significance of IRP2 phosphorylation.