Biosynthesis and Function of Base J

J碱基的生物合成和功能

• 批准号: 7154093
• 负责人: ROBERT S SABATINI
• 金额: --
• 依托单位: MARINE BIOLOGICAL LABORATORY
• 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 2006-12-02
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7154093
• 关键词: 5-((glucopyranosyloxy)methyl)uracil; ATP phosphohydrolase; Address; Affect; African; African Trypanosomiasis; Anabolism; Animals; Antigenic Variation; Appendix; 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

DESCRIPTION (provided by applicant): 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 DMA glycosylation 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.

描述（由申请人提供）：非洲锥虫（Trypanosoma brucei）是原生动物寄生虫，会导致人类致命的非洲昏睡病和动物的相关疾病。这些疾病对健康和经济造成毁灭性的后果。布氏锥虫的发病机制很大程度上取决于抗原变异现象。在哺乳动物宿主感染期间，大多数锥虫群体被对变异表面糖蛋白（VSG）外壳的免疫反应所破坏。在抗原变异的过程中，个体锥虫能够从数百个不同的 VSG 基因库中切换所表达的 VSG 基因，并逃避免疫破坏。为了表达，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。 VSG 沉默拷贝的选择性表达/抑制和转换机制尚不完全清楚。先前的分析表明，给定 VSG ES 的调节 与独特修饰的 DMA 碱基的缺失或存在相关，该碱基以胸腺嘧啶残基的糖基化为代表，称为碱基 J。J 与端粒 VSG 基因转录抑制的关联表明其在调节抗原变异中的作用。在本提案中，我们旨在通过定义与 J 相关的蛋白质/酶活性以及 J 掺入锥虫血流染色体中的后果来检查 J 活性的分子机制。为此，我们分离了一种蛋白质 JBP2，它调节 J-生物合成，决定修饰碱基的发育阶段特异性和端粒位点特异性合成。初步分析表明，JBP2 是必需基因，表明碱基 J 是血流染色体的必需修饰。该提案的广泛、长期目标是利用 JBP2 功能的生化和遗传分析作为工具，以增进我们对 T. brucei 中 J 功能的机制和生物学的理解。这些分析将使我们能够直接解决端粒 DMA 糖基化在抗原变异调节中的作用。 J 对寄生虫生存的潜在重要作用，以及其哺乳动物宿主中碱基 J 的缺失，表明具有广泛特异性和低毒性的抑制剂的设计具有吸引力的目标。 J-生物合成中涉及的酶和辅助因子将代表此类目标。这些研究可能有助于确定预防、治疗和诊断这些寄生虫引起的衰弱和致命疾病的新方法。