Control of gene expression by RNA conformational change during transcription

描述(申请人提供)：在原核生物和真核生物中都存在通过RNA结构调节基因表达的现象。细菌中基于RNA的调控的一种常见模式是核糖开关控制。这种类型的基因调控依赖于一个RNA序列形成两个不同结构的能力。因此，RNA的构象变化对核糖开关的调控至关重要。在转录过程中，小分子代谢物与新生mRNA中的适配子结构域结合，控制着该RNA形成的最终结构。一种结构通过终止转录或阻止翻译来抑制编码的蛋白质。另一种结构允许基因表达。其中一种核糖开关是大肠杆菌的维生素B12 btuB核糖开关。这种RNA控制外膜B12运输蛋白的表达，以响应细胞内维生素B12的浓度。为了实现这一点，相同的RNA序列必须根据B12与RNA的结合形成‘ON’或‘OFF’结构。传统上，生物物理方法被用来研究完整转录本中RNA结构的形成和重排。然而，核糖开关调节发生在转录过程中。为了了解核糖开关的作用机制，我们将研究转录过程中的折叠和重排。这项研究的好处是双重的。首先，它将提供对btuB系统的机械理解，并深入了解细菌中基于核糖开关的基因调控。核糖开关是广泛存在的遗传控制元件。其次，该提议将为理解转录过程中RNA的构象变化奠定一个一般的概念框架。 与公共卫生相关：这项研究将通过研究RNA在转录过程中的折叠，提供对细菌核糖开关功能的机械理解，与它在细胞中发生的方式相同。这些信息有望深入了解人类病原体中关键生化途径的调节。它还将为理解更复杂的、基于非编码RNA的高等生物体调控系统的机制提供一个概念框架和新的工具。

DESCRIPTION (provided by applicant): Regulation of gene expression by RNA structure occurs in both prokaryotic and eukaryotic organisms. One common mode of RNA based regulation in bacteria is riboswitch control. This type of gene regulation depends on the ability of one RNA sequence to form two different structures. Therefore, RNA conformational change is crucial to riboswitch regulation. Small molecule metabolite binding to an aptamer domain in nascent mRNA during transcription controls the final structure formed by that RNA. One structure represses the encoded proteins by terminating transcription or preventing translation. The alternative structure allows gene expression. One such riboswitch is the vitamin B12 btuB riboswitch of E. coli. This RNA controls the expression of an outer membrane B12 transport protein in response to the cellular concentration of vitamin B12. To accomplish this the same RNA sequence must form an 'on' or an 'off' structure dependent on B12 binding to the RNA. Traditionally, biophysical methods are used to study the formation and rearrangement of RNA structure in completed transcripts. However, riboswitch regulation occurs during transcription. To understand the mechanism of riboswitch function, folding and rearrangement will be studied during transcription. The benefit of this research is twofold. First it will provide a mechanistic understanding of the btuB system and insight into riboswitch based gene regulation in bacteria. Riboswitches are widespread genetic control elements. Second, the proposal will lay a general conceptual framework for the understanding of RNA conformational change during transcription. PUBLIC HEALTH RELEVANCE: This research will provide a mechanistic understanding of riboswitch function in bacteria by studying RNA folding during transcription, the same way it occurs in cells. This information is expected to give insight into the regulation of key biochemical pathways in human pathogens. It will also give a conceptual framework and new tools for understanding the mechanisms of more complex, non-coding RNA based regulatory systems in higher organisms.