Regulation of gene expression by oxygen

描述（由申请人提供）：确定细胞如何感知和适应环境中波动的氧气水平是生物学中的一个基本问题。我们的研究集中在兼性厌氧菌大肠杆菌对氧气可用性的调节策略上。这些研究使我们研究了两个Fe-S簇转录因子，FNR和IscR。利用Fe-S蛋白作为O2和其他生物相关氧化剂的传感器，利用了这些金属中心的特殊性质，并涉及到簇破坏和/或簇合成的调节。因此，我们的研究应该促进我们对Fe-S簇如何作为O2和其他重要氧化剂传感器的理解。全球调节因子FNR控制厌氧生长条件下的基因转录，并作为感知细胞氧水平的范例。维持活性构象所需的[4Fe-4S]2+团簇被O2依赖性去除后，FNR通过团簇破坏而失活。在此资助期内，将研究由该反应产生的载脂蛋白nr的命运，以便建立一个关于FNR如何在细胞水平上调节的综合模型。我们将测试apoFNR是否是在有氧生长条件下被CIpXP蛋白酶水解的FNR形式。此外，我们将确定当O2达到极限时，apoFNR是否可以被重新激活。最后，将对FNR的结构进行研究，以确定FNR的Fe-S簇如何改变其构象。IscR包含一个[2Fe-2S]簇，是Fe-S簇生物发生编码功能基因（isc操纵子）的抑制子。我们的假设是，IscR是细胞对Fe-S簇生物发生需求的传感器，它也参与基因表达的O2调控。IscR的[2Fe-2S]簇在感知细胞Fe-S簇状态中的作用将被研究。为了获得关于这些转录因子如何在有氧和无氧条件下重编程代谢的新见解，我们将研究FNR和IscR靶基因的调控，我们最近使用全基因组方法确定了这些靶基因。特别是，我们将研究厌氧条件下FNR拮抗IscR功能的机制，为O2调控基因表达提供一种新的策略。我们的研究将为包括致病生物在内的多种细菌感知O2的保守调控策略提供重要的新见解，并提供适用于所有生物的O2感知和基于Fe-S的感知的基本机制，当这些机制出错时可能导致人类疾病。

DESCRIPTION (provided by applicant): Determining how cell sense and adapt to fluctuating O2 levels in their environment is a fundamental problem in biology. Our studies focus on the regulatory strategies used by the facultative anaerobe E. coli to respond to O2 availability. These studies have led us to investigate two Fe-S cluster transcription factors, FNR and IscR. A picture is emerging that utilization of Fe-S proteins as sensors of O2 and other biologically relevant oxidants has taken advantage of the special properties of these metal centers and involves both regulation of cluster destruction and/or cluster synthesis. Thus, our studies should advance our understanding of how Fe-S clusters function as sensors of O2 and other important oxidants. The global regulator FNR controls transcription of genes under anaerobic growth conditions and serves as a paradigm for sensing cellular O2 levels. FNR is inactivated by cluster destruction upon the O2 dependent removal of its [4Fe-4S]2+ cluster that is required to maintain an active conformation. In this grant period, the fate of apoFNR that is produced from this reaction will be studied in order to develop a comprehensive model for how FNR is regulated at the cellular level. We will test whether apoFNR is the form of FNR that is proteolyzed by the CIpXP protease under aerobic growth conditions. In addition, we will determine whether apoFNR can be reactivated when O2 becomes limiting. Lastly, structural studies of FNR will be initiated to determine how the Fe-S cluster of FNR alters its conformation. IscR contains a [2Fe-2S] cluster and is a represser of genes encoding functions for Fe-S cluster biogenesis (isc operon). Our hypothesis is that IscR is a sensor of cellular demands for Fe-S cluster biogenesis and it is also involved in O2 regulation of gene expression. The role of the [2Fe-2S] cluster of IscR in sensing the Fe-S cluster status of cells will be investigated. To gain new insights into how these transcription factors reprogram metabolism under aerobic and anaerobic conditions, we will study the regulation of FNR and IscR target genes that we recently identified using a genome-wide approach. In particular, we will investigate the mechanism by which FNR antagonizes IscR function under anaerobic conditions to impart a new strategy for the O2 regulation of gene expression. Our studies should provide important new insights into the conserved regulatory strategies for sensing O2 that are used by a wide variety of bacteria including pathogenic organisms and provide fundamental mechanisms of O2 sensing and Fe-S based sensing that apply to all organisms, which when gone awry can cause human disease.