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（Brucei锥虫）是原生动物寄生虫，引起致命疾病 人类的非洲睡眠疾病和动物相关疾病。这些疾病具有毁灭性的 健康和经济后果。布鲁氏菌的发病机理至关依赖于现象 抗原变异。在哺乳动物宿主感染期间，大多数锥虫种群是 由于对变体表面糖蛋白（VSG）涂层的免疫反应破坏。在 抗原变异，单个锥虫能够切换从A表示的VSG基因 数百种不同VSG基因的曲目，并逃避免疫破坏。要表达，VSG 基因必须位于端粒表达位点（ES）中。但是，大约有20个ESS 一次只有一个活动。选择性表达/抑制和沉默的切换的机制 VSG的副本尚不完全理解。先前的分析表明，给定VSG ES的调节 与不存在或存在独特修饰的DMA碱基相关，以糖基化为代表 胸骨残基并称为碱基。J的关联与端粒VSG的转录抑制 基因表明其在调节抗原变异中的作用。在此提案中，我们旨在检查分子 通过定义与J和J和J和 J掺入血液形成锥虫的染色体中的后果。走向这个 最后，我们分离了一种调节J-Biosynsesis的蛋白质JBP2，确定了这两个发育 修饰碱基的特定阶段特异性和端粒位点特异性合成。初步分析表明 JBP2是一个必不可少的基因，表明碱基J是血液的必要修饰 染色体。该提案的广泛，长期目标是使用生化和遗传 JBP2的分析功能是提高我们对J功能机制和生物学的理解的工具 在T. Brucei。这些分析将使我们能够直接解决端粒Dmaglucosylation在 调节抗原变异。 J在寄生虫的生存中的潜在重要作用，以及 在其哺乳动物宿主中没有碱基J 广泛的特异性和低毒性。参与J-Biosynsis的酶和联合因素将代表这样的酶 目标。这些研究可能对识别预防，治疗和 这些寄生虫引起的衰弱和致命疾病的诊断。