RUI: Regulation of the Pyrimidine Pathway In Plants

抽象的mcb - 0078152。PI：彼得·d·纳吉。RNA复制是病毒发病机制的核心过程，以前的研究主要集中在启动子上。PI和其他人发现的新型顺式作用元件，如上调RNA合成的RNA复制增强子和下调RNA合成的RNA复制沉默子，改变了我们对RNA病毒复制的看法。这些RNA复制增强子和沉默子元件可能不仅在复制中发挥重要作用，而且还可能影响病毒的适应性和进化以及它们在受感染宿主中引起的症状。缺陷干扰（DI） RNA，由于其简单的基因组和强大的复制，是了解顺式作用元件在RNA复制中的作用的有吸引力的模型系统。DI rna是高度竞争性的寄生rna，与许多病毒感染有关。DI rna与其辅助病毒（亲本）竞争，导致辅助病毒的复制率降低，并经常导致宿主症状减轻。本研究需要验证的假设是，与辅助病毒相比，DI RNA具有优越的竞争力是由于(i) DI RNA中顺式作用元件的有利定位，如启动子和复制增强子，和/或（ii）在DI RNA中缺乏一些复制沉默元件，这些元件可能在DI RNA形成过程中已被删除。本研究使用tombusvirus（植物的模型+链RNA病毒）：(i)利用最近开发的无细胞复制酶系统表征复制增强子和沉默子元件；（ii）通过测试RNA增强子和沉默子元件对大肠杆菌中表达的tombusvirus复制酶蛋白模板结合的直接影响，阐明增强子介导的RNA转录刺激和沉默子介导的RNA转录抑制的机制。这些研究将有助于更好地理解被复制RNA上的序列对病毒RNA合成的调控。这些研究还将阐明某些不完全病毒变体减轻源自它们的原始完整病毒的感染的能力。这些变异被称为有缺陷的干扰RNA。它们来源于感染多种生物（包括植物）的病毒。

ABSTRACT MCB-0078152. PI: Peter D. Nagy. Previous work on RNA replication, a central process in viral pathogenesis, has focused on promoter elements. The discovery by the PI and others of novel cis-acting elements, such as RNA replication enhancers that up-regulate RNA synthesis and RNA replication silencers that down-regulate RNA synthesis, changes our view of RNA virus replication. These RNA replication enhancer and silencer elements may play major roles not only in replication, but they may also affect the fitness and evolution of viruses and the symptoms they cause in infected hosts. Defective interfering (DI) RNAs, due to their simple genomes and robust replication are attractive model systems for understanding the role of cis-acting elements in RNA replication. DI RNAs are highly competitive, parasitic RNAs associated with many virus infections. DI RNAs compete against their helper (parental) viruses, resulting in a decreased replication rate of the helper virus and frequently leading to symptom attenuation in the host. The hypothesis to be tested in this research is that the superior competitiveness of the DI RNAs relative to the helper virus is due to (i) favorable positioning of cis-acting elements, such as promoters and replication enhancers in DI RNAs, and/or (ii) the absence of some replication silencer elements in DI RNAs that may have been deleted during DI RNA formation. This research uses tombusviruses, model (+)-strand RNA viruses of plants, to: (i) characterize replication enhancer and silencer elements by using a recently developed cell-free replicase system; (ii) elucidate the mechanism of enhancer-mediated stimulation and silencer-mediated inhibition of RNA transcription through testing the direct effect of RNA enhancer and silencer elements on template binding by tombusvirus replicase proteins expressed in E. coli.These studies will lead to a better understanding of regulation of viral RNA synthesis by sequences on the RNA being copied. The studies will also elucidate the ability of certain incomplete viral variants to attenuate infections by the original, complete viruses from which they were derived. These variants are called defective interfering RNA's. They are derived from viruses that infect a wide range of organisms, including plants.