RNA CAPPING IN TRYPANOSOMES

描述：（由申请人提供）：我们的研究采用模型系统 非洲锥虫是人类昏睡病的病原体， 牛在过去的几年里，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，RNA代谢的调查，在这些 生物体在发现真核生物的新概念方面发挥了重要作用。 RNA生物学，如多顺反子转录，前mRNA的反式剪接， 和线粒体RNA编辑。该提案的主要目标仍然是获得 详细了解RNA的作用机制和生物学意义 在布氏锥虫中形成的。指导我们研究的基本原理如下。 首先，在T.布鲁氏菌m7 G添加到RNA分子的5'末端是相当重要的。 与其他真核生物不同。加帽发生在RNA上 聚合酶（pol）II转录物，即剪接前导（SL）RNA，以及 pol III转录物的特定子集，即U1、U2、U3和U4 snRNA，但 而不是其他更丰富的第三次政治调查记录，提出了根本问题， 转录选择的特异性。第二，存在两个 锥虫中不同的鸟苷酰转移酶多肽，每个都连接到一个 不同的领域，代表了一种新的物理组织的盖帽 装置，并指出这些生物体中RNA加帽的独特特征。 第三，核帽绑定复合物的鉴定提出了疑问 关于如何选择转录核出口发生在T。布鲁氏菌， 因为SL RNA和成熟核mRNA具有相同的帽。为下一 资助期建议的研究目的是：理解 压盖机部件的结构-功能方面， 以确定它们在RNA代谢中的生物学作用。2.定义序列 在各种加帽RNA的决定簇，以破译分子的细节 这是封端反应特异性的基础。3.开始分析 m7 G帽和核帽结合复合物之间的相互作用， 为了将帽结构连接到下游事件，包括反式剪接， 并将加帽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.