Biosynthesis and Function of Base J

J碱基的生物合成和功能

• 批准号: 7541351
• 负责人: ROBERT S SABATINI
• 金额: $ 31.61万
• 依托单位: UNIVERSITY OF GEORGIA
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-12-15 至 2010-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7541351
• 关键词: ATP phosphohydrolase; Address; Affect; African; African Trypanosomiasis; Anabolism; Animals; Antigenic Variation; Asses; Biochemical Genetics; Biological; Biological Process; Biology; Blood Circulation; Cells; Chromatin; Chromosomes; DNA Sequence Rearrangement; Development; Diagnosis; Disease; Dominant-Negative Mutation; Enzymes; Essential Genes; Family; Gene Expression; Gene Silencing; Genes; Goals; Human; Immune; Immune response; Immune system; Individual; Infection; Knock-out; Membrane Glycoproteins; Modification; Molecular; Nature; Nucleosomes; Parasites; Pathogenesis; Plant Roots; Population; Prevention approach; Process; Proteins; RNA Interference; Regulation; Repression; Research Personnel; Role; SWI2/SNF2; Site; Specificity; Staging; Structure; Thymine; Time; Toxic effect; Trypanosoma; Trypanosoma brucei brucei; Variant; base; chromatin remodeling; design; gene repression; genetic analysis; glycosylation; health economics; inhibitor/antagonist; knockout gene; mutant; novel strategies; pathogen; programs; selective expression; tool

African trypanosomes (Trypanosoma brucei) are protozoan parasites that cause a fatal disease known as African sleeping sickness in humans and related diseases in animals. These diseases have devastating health and economic consequences. Pathogenesis of T. brucei is critically dependent on the phenomena of antigenic variation. During infection of the mammalian host the majority of the trypanosome population is destroyed by the immune response to the Variant Surface Glycoprotein (VSG) coat. In the process of antigenic variation, individual trypanosomes are able to switch the VSG gene that is expressed, from a repertoire of several hundred different VSG genes, and evade immune destruction. To be expressed, a VSG gene has to be located within a telomeric expression site (ES). However, there are approximately 20 ESs and only one is active at a time. The mechanism of selective expression/repression and switching of silent copies of VSG is not entirely understood. Previous analysis indicates that regulation of a given VSG ES correlates with the absence or presence of a uniquely modified DMA base, represented by the glycosylation of thymine residues and called base J. The association of J with transcriptional repression of telomeric VSG genes suggests its role in regulation of antigenic variation. In this proposal we aim to examine the molecular mechanisms underlying J activity by defining the protein/enzymatic activities associated with J and the consequences of J incorporation within the chromosomes of bloodstream form trypanosomes. Towards this end we have isolated a protein, JBP2, that regulates J-biosynthesis, determining both the developmental stage-specific and telomeric site-specific synthesis of the modified base. Preliminary analysis indicates that JBP2 is an essential gene suggesting that base J is an essential modification of the bloodstream chromosome. The broad, long-term objectives of this proposal are to use the biochemical and genetic analyses of JBP2 function as tools to advance ourunderstanding of the mechanism and biology of J-function in T. brucei. These analyses will allow us to directly address the role of telomeric DMAglucosylation on the regulation of antigenic variation. The potentially significant role of J to the survival of the parasite, and the absence of base J in their mammalian hosts, indicates attractive targets for the design of inhibitors with broad specificity and low toxicity. Enzymes and co-factors involved in J-biosynthesis would represent such targets. These studies may prove useful in identifying novel approaches to prevention, treatment and diagnosis of the debilitating and deadly diseases caused by these parasites.

非洲锥虫（布氏锥虫）是原生动物寄生虫，可引起致命疾病，称为 人类非洲昏睡病和动物相关疾病。这些疾病具有毁灭性 健康和经济后果。布氏锥虫的发病机制主要取决于以下现象： 抗原变异。在哺乳动物宿主感染期间，大多数锥虫种群 被变异表面糖蛋白 (VSG) 外壳的免疫反应破坏。在这个过程中 由于抗原变异，个体锥虫能够将表达的 VSG 基因从 数百个不同的 VSG 基因库，并逃避免疫破坏。表达为 VSG 基因必须位于端粒表达位点 (ES) 内。然而，大约有 20 个 ES 并且一次只有一个处于活动状态。选择性表达/抑制和沉默切换机制 VSG 的副本尚未完全理解。先前的分析表明，给定 VSG ES 的调节 与糖基化代表的独特修饰 DMA 碱基的存在或不存在相关 胸腺嘧啶残基并称为碱基 J。J 与端粒 VSG 转录抑制的关联 基因表明其在调节抗原变异中的作用。在本提案中，我们的目标是检查分子 通过定义与 J 相关的蛋白质/酶活性和 J 活性的潜在机制 J 掺入血流染色体中形成锥虫的后果。朝这个方向 最终我们分离出了一种蛋白质 JBP2，它调节 J-生物合成，决定发育和发育 修饰碱基的阶段特异性和端粒位点特异性合成。初步分析表明 JBP2 是一个必需基因，表明碱基 J 是血液的重要修饰 染色体。该提案的广泛、长期目标是利用生化和遗传技术 JBP2 功能分析作为工具，促进我们对 J 功能机制和生物学的理解 在T. brucei。这些分析将使我们能够直接解决端粒 DMA 葡萄糖基化对 抗原变异的调节。 J 对寄生虫生存的潜在重要作用，以及 哺乳动物宿主中缺乏 J 碱基，表明具有吸引力的抑制剂设计目标 特异性广、毒性低。 J-生物合成中涉及的酶和辅助因子将代表这样的 目标。这些研究可能有助于确定预防、治疗和治疗的新方法。 诊断这些寄生虫引起的使人衰弱和致命的疾病。