RNA CAPPING IN TRYPANOSOMES

描述：(申请人提供)：我们的研究被用作模范系统 非洲锥虫，人类和纳加纳昏睡病的病原体 牛群。在过去的几年里，锥虫原虫已经达到了 单细胞病原体的模型系统，随着 基因组测序项目。此外，对这些动物体内RNA代谢的调查 生物体在发现真核生物的新概念方面起到了重要作用 RNA生物学，如多顺反子转录，前mRNAs的反式剪接， 和线粒体RNA编辑。这项提案的主要目标仍有待实现 详细了解RNA的作用机制和生物学意义 在布氏锥虫身上盖上帽子。指导我们研究的理论基础如下。 首先，在布氏锥虫m7G中，在rna分子的5‘端增加了相当多的 有别于其他真核生物的。封顶发生在RNA上 聚合酶(PolII)转录本，即剪接前导(SL)RNA，以及 PolIII转录本的一个特定子集，即U1、U2、U3和U4 SnRNAs，但 不是在其他更丰富的POL III成绩单上，引发了根本性的问题 关于成绩单选择的特殊性。第二，两个人的存在 锥虫体内不同的鸟苷酸转移酶多肽，每个都与一个 不同的域，代表了封顶的一种新的物理组织 装置，并指出了这些生物中核糖核酸封端的独特特征(S)。 第三，核帽结合复合体的识别提出了问题。 关于布氏锥虫是如何选择核出口的抄本的， 因为SL RNA和成熟的核mRNA都具有相同的帽子。下一次 资助期拟议研究的目的是：1.了解 封口机械部件的结构-功能方面 以确定它们在RNA新陈代谢中的生物学作用。2.定义顺序 不同封顶RNA中的决定因素，以破译分子细节 根据封顶反应的特异性。3.开始分析 M7G帽与核帽结合复合体之间的相互作用 将帽结构与下游事件链接起来，包括反式剪接 并将被封顶的mRNA从细胞核输出到细胞质中。

DESCRIPTION: (provided by the applicant): Our studies employ as a model system the African trypanosomes, the agents of sleeping sickness in man and nagana in cattle. In the last years, trypanosomatid protozoa have attained the status of model systems for unicellular pathogens, as underscored with the advent of genome sequencing projects. Furthermore, the survey of RNA metabolism in these organisms has been instrumental in the discovery of new concepts in eukaryotic RNA biology, such as polycistronic transcription, trans-splicing of pre-mRNAs, and mitochondrial RNA editing. The major goals of this proposal remain to gain a detailed understanding of the mechanism and biological significance of RNA capping in Trypanosoma brucei. The rationale guiding our studies is as follows. First, in T. brucei m7G addition to the 5' end of RNA molecules is quite distinct from that of other eukaryotic organisms. Capping occurs on RNA polymerase (pol) II transcripts, namely the spliced leader (SL) RNA, as well as a specific subset of pol III transcripts, namely U1, U2, U3 and U4 snRNAs, but not on other more abundant pol III transcripts, raising fundamental questions about the specificity of transcript selection. Second, the presence of two distinct guanylyltransferase polypeptides in trypanosomes, each linked to a different domain, represents a novel physical organization of the capping apparatus and points to unique feature(s) of RNA capping in these organisms. Third, the identification of the nuclear cap binding complex raises questions about how selection of transcripts for nuclear export takes place in T. brucei, as both SL RNA and mature nuclear mRNA possess the same cap. For the next funding period the proposed studies aim at: 1. Understanding structural-functional aspects of the components of the capping machinery in order to define their biological role in RNA metabolism. 2. Defining sequence determinants in various capped RNAs in order to decipher the molecular details underlying the specificity of the capping reaction. 3. Beginning an analysis of the interaction between the m7G cap and the nuclear cap binding complex in order to link the cap structure to downstream events, including trans-splicing and export of capped mRNA from the nucleus into the cytoplasm.