Suppression mechanism of Geminivirus-encoded TrAP protein

双生病毒编码的TrAP蛋白的抑制机制

• 批准号: 10294234
• 负责人: Xiuren Zhang
• 金额: $ 29.33万
• 依托单位: TEXAS A&M AGRILIFE RESEARCH
• 依托单位国家: 美国
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-12-21 至 2023-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10294234
• 关键词: Address; Affect; Animal Model; Antiviral resistance; Arabidopsis; Binding; Biochemical; Biological Models; Biotechnology; Chromatin; DNA; DNA Virus Infections; DNA Viruses; Defect; Defense Mechanisms; Deposition; Disease; Engineering; Enzymes; Epigenetic Process; Episome; Eukaryota; Exhibits; Factor V; Family; Functional disorder; Geminiviridae; Gene Expression; Gene Silencing; Gene Silencing Pathway; Genes; Genetic; Genetic Transcription; Goals; Health; Histones; Homologous Gene; Host Defense; Human; Immune response; Infection; Innate Immune Response; Innate Immune System; Interruption; Knowledge; Laboratories; Lysine; Mediating; Methylation; Modeling; Molecular; Natural Immunity; Nuclear; Pathogenicity; Pathway interactions; Physiological; Plant Model; Plant Viruses; Plants; Predisposition; Preventive measure; Proteins; Proteomics; RNA Interference; Reporting; Research; Role; Single Stranded DNA Virus; System; Testing; Viral; Viral Genes; Virus; Virus Diseases; Virus Latency; Work; arms race; base; cellular targeting; chromatin modification; combat; defense response; epigenetic silencing; histone demethylase; histone methyltransferase; human disease; in vivo; infancy; insight; loss of function; methyl group; mutant; novel; paralogous gene; pathogen; resistance mechanism; screening; tool; virus host interaction

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.

该研究的主要目的是从表观遗传学的角度阐明宿主先天免疫反应和病毒反防御反应的机制。真核生物已经进化出复杂的RNA沉默机制来防御入侵病毒。另一方面，包括感染人类的病毒在内的病毒编码称为病毒抑制子的蛋白质，以阻断沉默途径以逃避宿主监视。目前世界范围内对宿主-病毒相互作用的研究主要集中在转录后基因沉默（PTGS）的抗病毒作用和PTGS对病毒的抑制作用。虽然我们在PTGS水平上对病毒抑制的了解已经大大扩展，但我们在转录基因沉默（TGS）水平上对病毒抑制的理解非常差。在真核生物中，核DNA包裹在组蛋白八聚体上形成染色质。染色质甲基化不仅调节基因的复制和转录，而且控制病毒在人类和植物中的潜伏期，作为先天免疫系统发挥作用以限制入侵病原体。PI小组和其他实验室最近的研究表明，由模式生物拟南芥中的单链DNA病毒家族Geminivirus编码的TrAP抑制因子在遗传上干扰TGS途径。通过细胞因子的蛋白质组学筛选，PI的研究小组已经确定了组蛋白甲基转移酶（SUVH 4）和组蛋白脱甲基酶（REF 6），TGS途径中的两个关键效应子，是TrAP的新的真正靶点。这些结果和其他几个小组的工作导致了一个模型的概念化，即TGS作为防御入侵DNA病原体的防御机制，而病毒抑制剂可以通过直接抑制TGS整合剂来打破这种限制。为了解决该模型，PI提出：1）确定TrAP对SUVH特异性抑制作用的生化基础。主要研究者希望确定TrAP中参与与SUV H4相互作用的关键残基，并研究这些残基如何影响SUV H4功能并改变病毒致病性;主要研究者还将研究TrAP是否靶向SUV H4的遗传旁系同源物，如SUV H5和SUV H6，以调节双生病毒感染; 2）研究TrAP-REF 6相互作用在病毒感染中的功能和机制。PI实验室观察到REF 6与双生病毒染色质结合，并且ref 6的功能丧失突变体表现出对双生病毒感染的易感性降低。PI计划系统研究REF 6的生化特征及其在病毒转录和增殖中与TrAP的功能相互作用。这项拟议的研究将解决基本但人们知之甚少的机制，即组蛋白甲基转移酶和脱甲基酶如何协调赋予病毒潜伏期，以及DNA病毒如何选择劫持关键的TGS组分作为反防御反应。TrAP的抑制机制可用于定向治疗或预防措施，以解决由真核生物（包括人类）中的表观遗传功能障碍引起的生理病症。