Iron Regulation of Gene Expression

描述(申请人提供)：铁是许多蛋白质的功能所必需的，这些蛋白质是生物过程所必需的，包括电子转移、氧转移和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。过量的铁积累会导致肝硬变、心肌病、糖尿病、神经变性和癌症风险增加，而铁缺乏可能会导致儿童永久性的神经认知和运动障碍。由于铁的有害但有益的影响，哺乳动物细胞已经发展出高度调控的机制来感知、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与mRNAs中的铁反应元件(IRES)结合，编码与铁的吸收、隔离和利用有关的蛋白，并调节它们的翻译和降解。虽然IRP1和IRP2具有相似的序列，但它们在与单个mRNA的结合亲和力和铁调节其活性的机制方面有所不同。此外，Irp2-/-小鼠出现神经退行性疾病，而Irp1-/-小鼠没有明显的异常。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。我们的具体目标是：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基因的内源性编码序列缺失并替换为Irp1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编码序列是否可以挽救IRP2-/-小鼠的异常，2)确定信号IRP2铁介导的降解的机制，以及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.