INITIATION OF TRANSCRIPTION BY T7 RNA POLYMERASE

描述：转录的精确调控是细胞生物学的核心。 基因表达和基因组调控。这项研究的长期目标是 是理解转录的酶学，包括化学 启动子识别和转录起始的基础。的 来自T7相关噬菌体的小RNA聚合酶家族呈现 一个理想的模型系统，在其中研究，不仅是基本方面， 序列特异性识别DNA的转录，但也基本 聚合酶的一般机制。最后，这个家庭 简单的聚合酶与DNA和RNA大家族具有序列同源性 依赖性聚合酶，包括来自脊髓灰质炎、流感和 仙台病毒和来自B型肝炎和人类的逆转录酶 免疫缺陷病毒 T7模型系统的简单性很好地适用于针对 理解单个蛋白质-DNA官能团相互作用 导致DNA的特异性识别，并在一定程度上引发催化作用。 在DNA中有明确的位置。本建议的总体目标是 进一步完善启动子识别的新兴结构模型， 扩展该模型以包括关于早期阶段的机械细节 转录。强大的动力学和热力学 将官能团取代直接掺入 基于寡核苷酸的DNA模板允许详细探测关键的 蛋白质-DNA相互作用 光谱探针将被用来监测热力学和 通过RNA聚合酶的局部螺旋解链的动力学，而猝灭流 研究将用于跟踪RNA的有限转换合成。以下 制定一个启动机制的建议，具体的 干扰将被引入启动子中，以提供启动子之间的连接。 结构和功能。中的速率限制步骤的性质 引发也会受到反应条件改变的干扰， 以允许各种机械步骤的探测。的确切作用 模板链在定位底物的活性位点将被探索 通过启动子DNA的结构修饰。最后，修改 助催化剂将根据它们增加持续合成能力的能力来选择 在前几个核糖核苷酸的掺入过程中， 为了了解启动子释放和流产之间的关系， 骑自行车

DESCRIPTION: The precise regulation of transcription is central to cellular gene expression and genomic regulation. The long term goal of this research is to understand the enzymology of transcription, including the chemical basis of promoter recognition and the initiation of transcription. The family of small RNA polymerases from the T7 related bacteriophages presents an ideal model system in which to study, not only the fundamental aspects of sequence-specific recognition of DNA in transcription, but also the basic mechanisms of polymerases in general. Toward the latter end, this family of simple polymerases shows sequence homology to a large family of DNA and RNA dependent polymerases, including replicases from polio, influenza, and Sendai viruses and reverse transcriptases from hepatitis B and human immunodeficiency viruses. The simplicity of the T7 model system lends itself well to studies directed at understanding how individual protein-DNA functional group interactions lead to specific recognition of DNA and to the initiation of catalysis at a well-defined site in the DNA. The overall aim of this proposal is to further refine an emerging structural model for promoter recognition and to extend that model to include mechanistic detail regarding the early stages of transcription. The combination of powerful kinetic and thermodynamic assays with the direct incorporation of functional group substitutions into oligonucleotide based DNA templates allows detailed probing of critical protein-DNA interactions. A spectroscopic probe will be employed to monitor the thermodynamics and kinetics of local helix melting by the RNA polymerase, while quench-flow studies will be used to follow limited-turnover synthesis of RNA. Following the development of a mechanistic proposal for initiation, specific perturbations will be introduced into the promoter to provide a link between structure and function. The nature of the rate limiting step(s) in initiation will also be perturbed by alteration of the reaction conditions, to allow probes of various mechanistic steps. The precise role of the template strand in positioning substrate at the active site will be explored via structural modifications of the promoter DNA. Finally, modifications in the promoter will be selected for their ability to increase the processivity of transcription during incorporation of the first few ribonucleotides, in order to understand relationships between promoter release and abortive cycling.