INHIBITION OF STAT TRANSCRIPTION BY TOXOPLASMA

弓形虫是一种广泛存在的动物寄生虫，可引起人畜共患传染病。 人类。尽管健康成年人的急性感染通常在没有 严重后果，感染免疫功能低下的个人可导致严重 并发症。此外，因为慢性感染不会被免疫系统清除 或通过正常的抗生素治疗，个人终生保持慢性感染。 存在可重新激活的半休眠组织囊肿易感染 在免疫力减弱的情况下，个体对并发症的风险很高。其中一个关键是 弓形虫能够在宿主中持续存在的特征是阻断免疫的能力 反应，从而防止寄生虫清除。在这些路径中， 被弓形虫感染扰乱的是信号转导和转录激活因子 (STAT)转录因子家族。弓形虫感染的控制依赖于激活 通过干扰素-γ的STAT1，这是上调两者的抗菌途径所必需的 造血细胞和非造血细胞。然而，当细胞感染T. 在遇到干扰素-γ之前，这种寄生虫能够阻断STAT1介导的 转录导致减少对感染的控制。基因表达的全球分析 发现大多数干扰素-γ激活的基因被先前感染T。 贡地。STAT1信号通路的阻断在啮齿动物和人类细胞中都存在，尽管 这一特征的分子基础之前还没有确定。 在初步研究中，我们已经鉴定出一种能与磷酸化的弓形虫结合的蛋白质。 STAT1二聚体并阻止下游基因的激活。这个效应器被称为T. Gondii STAT转录抑制因子阻断干扰素-γ诱导的基因表达 由STAT1介导。TgIST既是阻止STAT1的必要条件，也是充分条件。 在小鼠和人类细胞中介导转录。TgIST与宿主抑制物结合 改变染色质结构的复合体。拟议的研究将确定东道主的角色 染色质修饰剂利用基因调控STAT1转录复合体 CRISPR/Cas9结合各种报告分析的干扰。此外，我们还将 实施各种细胞、生化和遗传方法来定义结构域 TgIST是出口和贩运到宿主细胞核所必需的，在宿主细胞核中，TgIST是活跃的。

Toxoplasma gondii is a widespread parasite of animals that causes zoonotic infection in humans. Although acute infections in healthy adults are normally resolved without serious consequences, infection of immunocompromised individuals can lead to serious complications. Additionally, because chronic infections are not cleared by the immune system or by normal antibiotic treatment, individuals remain chronically infected for life. The presence of semi-dormant tissue cysts that can reactivate predisposes infected individuals to the risk of complications in the event of waning immunity. One of the key features of T. gondii that enables it to persist in the host is the ability to block immune responses, and thereby prevent clearance of the parasite. Among the pathways that are perturbed by T. gondii infection are the signal transducer and activator of transcription (STAT) family of transcription factors. Control of T. gondii infection relies on activation of STAT1 by IFN-γ, which is essential to upregulate antimicrobial pathways in both hematopoietic and non-hematopoietic cells. However, when cells are infected by T. gondii before encountering IFN-γ, the parasite is able to block STAT1-mediated transcription resulting in reduced control of infection. Global analysis of gene expression reveals that the majority of IFN-γ-activated genes are blocked by prior infection with T. gondii. The block in STAT1 signaling occurs in both rodent and human cells, although the molecular basis for this trait has not been previously identified. In preliminary studies we have identified a T. gondii protein that binds to phosphorylated STAT1 dimers and prevents activation of downstream genes. This effector, known as T. gondii Inhibitor of STAT Transcription (TgIST) blocks IFN-γ-induced gene expression mediated by STAT1. TgIST is both necessary and sufficient for blocking STAT1- mediated transcription in mouse and human cells. TgIST binds to a host repressor complex that alters chromatin structure. The proposed studies will define the role of host chromatin modifiers in modulating STAT1 transcriptional complexes using gene disruption by CRISPR/Cas9 combined with various reporter assays. Additionally, we will implement a variety of cellular, biochemical, and genetic methods to define the domains necessary for export and trafficking of TgIST to the host cell nucleus, where it is active.