An Oxygen-Sensing Network Involving Heme and Chaperones

描述（由申请人提供）：本提案的广泛，长期目标是阐明真核生物中控制氧传感，血红素信号和伴侣作用的分子机制。在许多生物体中，氧气对于维持关键的细胞功能至关重要，而血红素是氧气感知和利用的核心。在人类中，氧气感知和调节缺陷或血红素合成缺陷导致人类严重疾病，包括癌症、卟啉症、呼吸系统和血液系统疾病。因此，了解氧气是如何被感知的，以及血红素和分子伴侣如何促进氧气和全球基因调控，对改善人类健康至关重要。本研究以酵母为模型系统，研究真核生物的氧感应、血红素信号和伴侣作用。在酵母中，血红素通过控制血红素激活蛋白Hapl的转录活性来调节许多基因的氧调节。分子伴侣Hsp90和Hsp70结合Hapl并促进血红素对Hapl活性的调节。本实验将严格检验以下假设：(1)Hapl-multichaperone复合体直接与DNA结合，促进转录失活和抑制；(2)通过血红素合成来感知氧水平；(3)血红素和Hapl在全局氧传感和全局转录调控中起关键作用。

DESCRIPTION (provided by applicant): The broad, long-term objective of this proposal is to elucidate the molecular mechanisms governing oxygen sensing, heme signaling and chaperone action in eukaryotes. Oxygen is vital for maintaining critical cellular functions in many living organisms, and heme is central to oxygen sensing and utilization. In humans, defects in oxygen sensing and regulation or in heme synthesis cause serious diseases in humans, including cancers, porphyrias, and respiratory and hematological diseases. Thus, understanding how oxygen is sensed and how heme and molecular chaperones promote oxygen and global gene regulation is important for improving human health. This proposal uses yeast as a model system for investigating oxygen sensing, heme signaling and chaperone action in eukaryotes. In yeast, heme mediates oxygen regulation of many genes by controlling the transcriptional activity of the heme activator protein Hapl. Molecular chaperones Hsp90 and Hsp70 bind to Hapl and promote heme regulation of Hapl activity. Experiments in this proposal will rigorously test the following hypotheses: (1) Hapl-multichaperone complexes bind directly to DNA and promote transcriptional aactivation and repression; (2) the oxygen level is sensed through heme synthesis; and (3) heme and Hapl play key roles in global oxygen sensing and global transcription regulation. The specific aims are (1) to clarify and compare the molecular mechanisms by which Hapl activates and represses transcription, (2) to dissect the molecular mechanism by which intracellular heme level is linked to oxygen level, and (3) to determine the global roles of heme and Hapl in oxygen sensing and regulation. Biochemical, genetic, and advanced microarray technologies and computational algorithms will be used to accomplish these aims. The gained knowledge should facilitate the understanding of the molecular mechanisms of oxygen sensing, heme signaling and chaperone action in higher eukaryotes.