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不断变化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供应的反应中所使用的调控策略。这些研究使我们对两个Fe-S簇转录因子FnR和Iscr进行了研究。有一幅图显示，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，涉及到簇破坏和/或簇合成的调节。因此，我们的研究将促进我们对Fe-S团簇如何作为O2和其他重要氧化剂的传感器的理解。全球调控因子FNR在厌氧生长条件下控制基因的转录，并作为检测细胞O2水平的范例。FNR在其维持活性构象所需的[4Fe-4S]2+簇被O2依赖的移除后被簇破坏而失活。在这一授权期内，将研究这种反应产生的apoFNR的命运，以便开发一个在细胞水平上如何调节FNR的综合模型。我们将测试apoFNR是否是在有氧生长条件下被CIpXP酶降解的FNR的形式。此外，我们将确定当氧气变得有限时，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，是编码铁-S簇生物发生(ISC操纵子)功能的基因的抑制子。我们的假设是，Iscr是铁-S簇生物发生过程中细胞需求的传感器，它也参与了O2对基因表达的调节。将研究Iscr的[2Fe-2S]簇在感知细胞的Fe-S簇状态中的作用。为了对这些转录因子如何在有氧和无氧条件下重新编程代谢有新的见解，我们将使用全基因组方法研究我们最近发现的FNR和ISCR靶基因的调控。特别是，我们将研究FNR在厌氧条件下拮抗ISCR功能的机制，为O2调控基因表达提供新的策略。我们的研究将为包括病原体在内的各种细菌使用的保守的O2传感调控策略提供重要的新见解，并提供适用于所有生物体的O2传感和基于Fe-S的传感的基本机制，当出错时，这些机制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.