The role of CITFA-2 in RNA polymerase I transcription in Trypanosoma brucei

描述(申请人提供)：布氏锥虫在撒哈拉以南非洲由采采蝇传播，是人类非洲锥虫病的病原体，又称睡眠病，造成相当大的疾病负担和生命损失。布鲁氏毛滴虫还会引起Nagana，这是一种相应的家畜疾病，在它流行的地区对农业和经济发展造成了障碍。由于缺乏安全、有效和易于管理的治疗选择，对这种疾病的控制充其量是微乎其微的。此外，由于抗药性不断增强，人们担心该病可能会像过去那样再次出现。因此，迫切需要对这种寄生虫有更多的了解。布氏毛滴虫已经进化出许多免疫逃避技术，使其非常适合各种哺乳动物宿主，其中最值得注意的是它的抗原变异能力。在哺乳动物的血液中，布氏毛滴虫完全被一层厚厚的变异表面糖蛋白(VSG)所覆盖，VSG是从一个大基因家族的单个基因中表达的。抗原变异是通过周期性地切换到不同的VSG基因的表达来实现的，这会导致新的寄生虫种群逃脱免疫系统的检测。此外，即使在没有免疫力的情况下(即在培养中)，VSG的表达对于寄生虫的生存也是必不可少的。本项目的主要目的是研究VSG转录所必需的I类转录因子A必需亚基2(CITFA)的特定功能。初步数据表明，CITFA-2与启动子直接接触，含量低于其他CITFA亚基，提示它在单等位基因VSG的表达调控中起着关键作用。此外，CITFA-2的包含似乎定义了活性的CITFA复合体。因此，CITFA-2可以作为分离和鉴定与活性CITFA特异结合的蛋白质的工具。

DESCRIPTION (provided by applicant): Trypanosoma brucei is transmitted by the Tsetse fly in sub-Saharan Africa and is the causative agent of Human African Trypanosomiasis, also known as Sleeping Sickness, which is responsible for a considerable disease burden and loss of life. T. brucei also causes Nagana, a corresponding disease in livestock, which creates a barrier to agricultural and economic progress in the areas it is endemic. Control of this disease is tenuous, at best, due to a lack of safe, effective, and easily administered treatment options. Additionally, due to increasing drug resistance, there is concern that re-emergence of the disease may occur, as has happened in the past. It is therefore imperative that additional understanding of this parasite be gained. T. brucei has evolved numerous immune evasion techniques that make it well suited to its various mammalian hosts, most notable of which is its ability of antigenic variation. In the mammalian bloodstream, T. brucei is completely covered by a dense coat of variant surface glycoprotein (VSG) that is expressed from a single gene drawn from a large gene family. Antigenic variation is achieved by periodically switching to the expression of a different VSG gene, which results in a new parasite population which escapes detection by the immune system. Moreover, VSG expression is essential for parasite viability even in the absence of immunological forces (i.e. in culture). The main goal of this project is to study the specific function of the essential subunit 2 of class I transcription factor A (CITFA) tht is absolutely required for VSG transcription. Preliminary data indicates that CITFA-2 directly contacts the promoter and is less abundant than other CITFA subunits, suggesting that it plays a key role in regulating monoallelic VSG expression. Additionally, CITFA-2 inclusion appears to define the active CITFA complex. CITFA-2 can therefore be used as a tool for isolation and identification of proteins which associate specifically with active CITFA.