Control of VSG pre-mRNA processing in infectious Trypanosoma brucei

项目摘要 本申请的重点是原生动物寄生虫布氏锥虫， 哺乳动物宿主通过采采蝇，并且由于有效的免疫逃避，引起慢性和致命的感染， 特别是非洲人的昏睡病和牛的长形病。而人类非洲锥虫 最近已经下降，牲畜感染仍然普遍，并对经济产生深远影响。 撒哈拉以南非洲的发展。没有疫苗和治疗药物有严重的副作用， 降低功效。因此，迫切需要进行研究，以更好地了解这些生物学 病原体及其在宿主体内生存的机制。t.布鲁氏菌经历了复杂的生命周期 哺乳动物宿主和吸血采采蝇媒介之间的关系。为了应对不断变化的环境， 寄生虫通过不同的生命周期形式过渡，这些形式已经进化以确保生存和成功 传输到下一个主机。例如，当T.布鲁塞表示， 变异表面糖蛋白（VSG）外壳，这是抗原变异的范例。虽然有 基因组中有数百个VSG基因，血流形式的VSG表达仅限于约15个中的1个 特化端粒血流表达位点（BES）。在昆虫的唾液腺中介导亚循环 锥虫被VSG的一个特定的小子集，即亚循环VSG（mVSG）所覆盖， 使其能够传播给脊椎动物宿主。mVSG表达由未知机制触发， 在不存在采采蝇组织的情况下，通过诱导RNA结合蛋白6的表达， （RBP6）。这个应用程序的一个主要目标将是检查锥虫如何接收指令开始 合成mVSG外壳，以及每个细胞何时开始表达单个mVSG。我们将使用单细胞 RNA-Seq和长期活细胞成像来回答机制问题。此外，我们的新发现， mVSG基因编码一个外显子剪接增强子，揭示了VSG调节的全新方面， 可以解释严格控制的成熟mRNA的极高产量。

Project Summary This application focuses on the protozoan parasite Trypanosoma brucei, which is transmitted among mammalian hosts by tsetse-flies and, due to effective immune evasion, causes chronic and lethal infections, specifically African sleeping-sickness in humans and nagana in cattle. Whereas human African trypanosomiasis has been declining recently, livestock infections remain prevalent and have a profound effect on economic development in sub-Saharan Africa. There are no vaccines and therapeutic drugs have serious side effects and decreasing efficacy. Thus, there is a pressing need for research to better understand the biology of these pathogens and the mechanisms they use to survive within their hosts. T. brucei undergoes a complex life cycle between the mammalian host and the blood-feeding tsetse fly vector. To cope with the changing environment, the parasite transitions through distinct life cycle forms that have evolved to assure survival and successful transmission to the next host. For instance, when residing in the mammalian host, T. brucei expresses a variant surface glycoprotein (VSG) coat, which is the paradigm for antigenic variation. Although there are hundreds of VSG genes in the genome, bloodstream-form VSG expression is restricted to 1 of about 15 specialized telomeric bloodstream expression sites (BES). In the salivary glands of the insect vector metacyclic trypanosomes are covered by a specific and small subset of VSGs, the metacyclic VSGs (mVSGs), which enable transmission to a vertebrate host. mVSG expression is triggered by an unknown mechanism and in vitro can be achieved in the absence of tsetse tissues by induced expression of the RNA-binding protein 6 (RBP6). One major goal of this application will be to examine how trypanosomes receive instructions to begin synthesizing the mVSG coat, and when each cell begins expressing a single mVSG. We will use single-cell RNA-Seq and long-term live-cell imaging to answer mechanistic questions. In addition, our novel finding that mVSG genes encode an exonic splicing enhancer exposed a completely new aspect of VSG regulation and may explain the tightly-controlled extremely high output of mature mRNAs.