Suppression mechanism of Geminivirus-encoded TrAP protein

这项研究的主要目的是阐明宿主先天免疫的机制。 在表观遗传水平上的反应和病毒反防御反应。真核生物进化出了复杂的 RNA沉默防御入侵病毒的机制。另一方面，包括感染病毒在内的病毒 人类编码被称为病毒抑制物的蛋白质，以阻止沉默途径逃避宿主 监视系统。目前国际上对宿主-病毒相互作用的研究主要集中在病毒的抗病毒作用上。 转录后基因沉默(PTGS)及其病毒抑制。虽然我们对病毒的了解 PTGS水平的抑制已经大大扩大，我们对病毒抑制的理解在 转录基因沉默(TGS)水平很低。在真核生物中，核DNA被包裹在 组蛋白八聚体形成染色质。染色质甲基化不仅调节基因复制和 转录，但也控制着病毒在人类和植物中的潜伏期，起到先天免疫的作用 限制入侵病原体的系统。PI的团队和其他实验室最近的研究表明 阐明了由GeminiVirus编码的陷阱抑制因子，GeminiVirus是单链DNA病毒家族中的一员 模式生物拟南芥，从基因上干扰TGS途径。通过对细胞蛋白质组的筛选 因素，Pi的小组已经确定了一个组蛋白甲基转移酶(SUVH4)和一个组蛋白去甲基酶 (REF6)是TGS途径中的两个关键效应因子，是TRAP新的真正靶标。这些成果和工作 来自其他几个小组的意见导致了TGS作为防御机制的模型的概念化 防御入侵的DNA病原体，而病毒抑制物可以通过直接抑制 TGS积分器。为了解决这一模型，PI建议：1)确定特定的生化基础 TRAP对SUVH的抑制作用。PI希望查明参与TRAIN的关键残留物 与SUVH4相互作用并研究残基如何影响SUVH4功能和改变病毒 致病性；PI还将研究TRAP是否针对SUVH4的遗传同源基因，如SUVH5和 SUVH6调控双生病毒感染；2)研究TRAP-REF6的功能和机制 病毒感染中的相互作用。PI实验室观察到REF6与双生病毒染色质结合并 功能缺失的ref6突变体对双生病毒感染的易感性降低。私家侦探计划 系统研究REF6的生化特性及其与TRAP在病毒转录中的功能相互作用 和乘法。拟议的研究将解决基本但鲜为人知的机制如何 组蛋白甲基转移酶和去甲基酶协同赋予病毒潜伏期以及DNA病毒如何参与 劫持关键的TGS组件作为反防御反应。陷阱抑制机制可以 被用于定向治疗或预防措施，以解决由以下原因引起的生理障碍 包括人类在内的真核生物的表观遗传功能障碍。

The primary goal of the proposed research is to elucidate the mechanism of host innate immune responses and viral counter-defense responses at an epigenetic level. Eukaryotes have evolved sophisticated mechanisms of RNA silencing to defense invasive viruses. On the other hand, viruses including those infecting humans encode proteins, referred to as viral suppressors, to block silencing pathways to evade host surveillance. The prevailing worldwide study on host-virus interaction focuses on the antivirus role of posttranscriptional gene silencing (PTGS) and viral suppression of PTGS. While our knowledge of viral suppression at the PTGS level has been drastically expanded, our understanding of viral suppression at the level of transcriptional gene silencing (TGS) is very poor. In eukaryotes, the nuclear DNA is wrapped onto histone octamers to form a chromatin. Chromatin methylation not only regulates gene replication and transcription, but also controls the latency of viruses in human and plants, functioning as an innate immune system to restrict invasive pathogens. Recent research from the PI's group and other laboratories has illuminated that TrAP suppressor encoded by Geminivirus, a family of single-stranded DNA viruses in the model organism Arabidopsis, genetically interferes with the TGS pathway. By proteomic screening of cellular factors, the PI's group has identified that a histone methyltransferase (SUVH4) and a histone demethylase (REF6), two key effectors in the TGS pathway, are new bona fide targets by TrAP. These results and work from several other groups led to conceptualization of a model that TGS serves as a defense mechanism to defend invasive DNA pathogens, whereas viral suppressors can break this restriction by directly inhibiting the TGS integrators. To address this model, the PI proposes: 1) to determine the biochemical basis for specific inhibitory effect of TrAP on SUVH. The PI wishes to pinpoint the critical residues of TrAP that participate in the interaction with SUVH4 and investigate how the residues affect SUVH4 function and alter the viral pathogenicity; The PI will also study whether TrAP targets the genetic paralogs of SUVH4 such as SUVH5 and SUVH6 to regulate Geminivirus infection; and 2) to investigate function and mechanism of TrAP-REF6 interaction in viral infection. The PI laboratory has observed that REF6 binds to Geminivirus chromatin and loss-of-function mutants of ref6 exhibit reduced susceptibility to Geminivirus infection. The PI plans to systemically study the biochemical features of REF6 and its functional interaction of TrAP in viral transcription and multiplication. The proposed study will address the fundamental but poorly understood mechanism how histone methyltransferases and demethylases coordinately confer viral latency and how DNA virus co-opts to hijack the critical TGS components as counter-defense responses. The suppression mechanism of TrAP may be exploited for directed therapies or preventative measures to address physiological disorders that arise from epigenetic dysfunction in eukaryotes including human.