Antigenic Switching by VSG Gene Conversion in T. brucei

描述（由申请人提供）：布氏锥虫是一种真核生物， 通过抗原变异逃避哺乳动物宿主免疫反应的寄生虫： 改变其变异表面糖蛋白（vsG）？外套？通过交替 表达其基因组中数百个高度分化的VSG基因中的一个 VSG开关通过很少研究的基因转换过程发生。在此为 提出了一种新的策略，用选择性标记取代VSG ORF， 研究影响VSG盒基因转化的参数。药物 选择将检测无启动子标记与活性标记的重组。 VSG，允许分离和研究罕见的基因转换事件。的 假设内部VSGS与端粒VSGS重组率不同 将通过测量来自置于每种类型的标记的基因转换来进行评估 的网站。用沉默端粒VSG上游的潜在启动子创建细胞系 会发现什么呢沉默？开关，这可能会打乱并增加 VSGS的可用性？首选？染色体定位记者 可以改变构建体以测试VSG的保守序列基序的作用 基因转换盒对VSG转换速率和顺序的影响。 染色体背景和局部序列元件对 重组将被分开。对VSG基因的深入了解 转换将允许开发更准确的模型来解释和 预测抗原变异的模式这项工作是高度相关的， 宿主-病原体相互作用，特别是锥虫和疟疾寄生虫。

DESCRIPTION (provided by the applicant): Trypanosoma brucei is a eukaryotic parasite that evades mammalian host immune response by antigenic variation: changing its Variant Surface Glycoprotein (vsG) ?coat? by alternatively expressing one among hundreds of highly diverged VSG genes in its genome Most VSG switches occur by the little-studied process of gene conversion. Here, a new strategy is proposed, replacing VSG ORFs with selectable markers, to investigate parameters affecting gene conversion of VSG cassettes. Drug selection will detect recombination of promoter-less markers with the active VSG, allowing isolation and study of rare gene conversion events. The hypothesis that recombination rates differ for internal versus telomeric VSGS will be evaluated by measuring gene conversion from markers placed at each type of site. Creating lines with latent promoters upstream of silent telomeric VSGs will detect otherwise ?silent? switches, which might shuffle and increase the availability of VSGS at ?preferred? chromosornal locations. The reporter constructs can be altered to test the role of conserved sequence motifs of VSG gene conversion cassettes for effects on the rates and order of VSG switching. The influence of chromosomal context and local sequence elements on recombination will be teased apart. A thorough understanding of VSG gene conversion will allow development of more accurate models to explain and predict patterns of antigenic variation. This work is highly relevant to host-pathogen interactions, especially in trypanosomes and malaria parasites.