Control of gene expression by RNA conformational change during transcription

描述（由申请人提供）：在原核生物和真核生物中都存在RNA结构对基因表达的调节。细菌中基于RNA的调节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序列形成两种不同结构的能力。因此，RNA构象变化对核糖开关调控至关重要。小分子代谢物在转录过程中与新生mRNA中的适体结构域结合，控制该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蛋白。替代结构允许基因表达。一种这样的核糖开关是大肠杆菌的维生素B12 btuB核糖开关。杆菌这种RNA控制外膜B12转运蛋白的表达，以响应维生素B12的细胞浓度。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“开”或“关”结构。传统上，生物物理方法用于研究完整转录物中RNA结构的形成和重排。然而，核糖开关调控发生在转录过程中。为了理解核糖开关功能的机制，将在转录过程中研究折叠和重排。这项研究的好处是双重的。首先，它将提供一个btuB系统的机械理解和深入了解核糖开关为基础的基因调控细菌。核糖开关是广泛存在的遗传控制元件。其次，该方案将为理解转录过程中RNA构象变化奠定一个总体概念框架。

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.