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其环境中波动的O2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E.大肠杆菌对O2的反应。这些研究引导我们研究两个Fe-S簇转录因子，FNR和IscR。一个图片正在出现，利用Fe-S蛋白作为传感器的O2和其他生物相关的氧化剂已经利用了这些金属中心的特殊性质，并涉及到集群破坏和/或集群合成的调节。因此，我们的研究应该推进我们的理解如何Fe-S簇作为传感器的O2和其他重要的氧化剂。 全局调节因子FNR控制厌氧生长条件下的基因转录，并作为感知细胞O2水平的范例。FNR通过依赖于O2的[4Fe-4S]2+簇的去除而被簇破坏而失活，这是保持活性构象所必需的。在此期间，将研究从该反应产生的apoFNR的命运，以开发一个全面的模型来研究FNR如何在细胞水平上进行调节。我们将测试apoFNR是否是在需氧生长条件下被ClpXP蛋白酶蛋白水解的FNR形式。此外，我们将确定当O2变得有限时apoFNR是否可以重新激活。最后，将启动FNR的结构研究，以确定FNR的Fe-S簇如何改变其构象。 IscR含有一个[2Fe-2S]簇，并且是编码Fe-S簇生物发生功能的基因（isc操纵子）的阻遏物。我们的假设是，IscR是一个传感器的细胞需求的Fe-S簇的生物合成，它也参与了O2的基因表达调控。将研究IscR的[2Fe-2S]簇在感知细胞的Fe-S簇状态中的作用。为了获得这些转录因子如何在有氧和无氧条件下重新编程代谢的新见解，我们将研究我们最近使用全基因组方法确定的FNR和IscR靶基因的调节。特别是，我们将研究的机制，FNR拮抗IscR功能在厌氧条件下传递一个新的策略O2基因表达的调控。我们的研究应该提供重要的新的见解保守的监管策略，用于传感O2的各种细菌，包括病原体，并提供O2传感和Fe-S为基础的传感，适用于所有生物体的基本机制，当出错时，可能会导致人类疾病。

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.