REGULATION OF GENE EXPRESSION BY OXYGEN

描述：(申请人摘要) 确定细胞如何感知和适应体内O2水平的波动 环境是生物学中的一个基本问题。对于许多原核生物和 对于真核生物来说，对氧气水平的感知是确保 充足的能量供应，以及避免氧气的毒性影响。在……里面 近年来，已有研究表明，FNR家族的许多成员 转录因子在广泛的无氧生活方式中发挥关键作用 原核生物的一群，在氧气感应中起作用。因此，通过破译fnar 活动对氧气供应的反应，我们将获得基本的 关于对儿童的成长和生存至关重要的过程的信息 兼性微生物。此外，我们的研究应该为以下方面提供关键的见解 氧气传感的一些一般特性可以应用于这两个 真核细胞和原核细胞。 在最佳研究的大肠杆菌案例中，FNR包含一个[4Fe-4S]2簇 这是二聚化和位点特异性DNA结合所必需的。这[4Fe-4S]2 团簇对氧敏感，其向[2Fe-21S]2的转化率降低 体外二聚化和DNA结合。解释FNR活性是如何受到调节的 在体内，我们认为FNR在厌氧条件下大部分是活跃的，因为 [4Fe-4S]2团簇是稳定的，而在有氧的情况下，我们认为 该FNR由于转化为[2Fe-2S]2中间体或 可能是一种缺少簇的apo-fnr形式。以确定是否 [4Fe-4S]2簇转化足以解释FNR是如何失活的 在体内的有氧条件下，我们将确定FNR失活的途径 在活体内。要确定[4Fe-4S]2团簇的存在如何增加FNR 活性，我们将检验[4Fe-4S]2团簇需要 获得适合二聚化的构象。为了进一步定义 FNR作为全球转录调节因子的作用我们将描述以下区域 FNR参与转录激活。我们的研究应该为 感知氧分压变化的保守调节策略 原核生物的种类，包括几种致病生物。

DESCRIPTION: (Applicant's abstract) Determining how cells sense and adapt to fluctuating O2 levels in their environment is a fundamental problem in biology. For many prokaryotic and eucaryotic organism, the sensing of oxygen levels is essential to ensure an adequate supply of energy as well as to avoid the toxic effects of oxygen. In recent years, it has been shown that many members of the FNR family of transcription factors that play a key role in the anaerobic lifestyle of a wide group of prokaryotes, function in oxygen sensing. Thus by deciphering how FNAR activity responds to oxygen availability, we will obtain fundamental information on a process that is critical to the growth and survival of facultative microbes. In addition, our studies should provide key insights into some general properties of oxygen sensing that can be applied to both eucaryotic and prokaryotic cells. In the best-studies case of Escherichia coli, FNR contains a [4Fe-4S]+2 cluster that is required for dimerization and site-specific DNA binding. This [4Fe-4S]+2 cluster is oxygen sensitive and its conversion to a [2Fe-21S]+2 decreases dimerization and DNA binding in vitro. To explain how FNR activity is regulated in vivo, we propose that FNR is largely active under anaerobic conditions because the [4Fe-4S]+2 cluster is stable whereas, in the presence of oxygen, we propose that FNR is largely inactive due to its conversion to a [2Fe-2S]+2 intermediate or possibly an apo-FNR form that lacks a cluster. To determine whether the [4Fe-4S]+2 cluster conversion is sufficient to explain how FNR is inactivated under aerobic conditions in vivo, we will define the pathway of FNR inactivation in vivo. To determine how the presence of the [4Fe-4S]+2 cluster increases FNR activity, we will test the hypothesis that the [4Fe-4S]+2 cluster is required to achieve a conformation that is competent for dimerization. To further define the role of FNR as a global regulator of transcription we will characterize the regions of FNR involved in transcription activation. Our studies should rovide insights into conserved regulatory strategies for sensing changes in oxygen tension by a wide variety of prokaryotes including several pathogenic organisms.