Mechanisms of Gene Regulation by EBV EBNA-1 Protein

EBV EBNA-1蛋白的基因调控机制

• 批准号: 7621316
• 负责人: JEFFERY T SAMPLE
• 金额: $ 38.78万
• 依托单位: PENNSYLVANIA STATE UNIV HERSHEY MED CTR
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-08-01 至 2011-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7621316
• 关键词: Acquired Immunodeficiency Syndrome; Acute; Address; Apoptotic; B-Lymphocytes; Binding; Binding Sites; Biological Assay; Biology; Cancer Etiology; Cell division; Cells; Coupled; Cytotoxic T-Lymphocytes; Development; Disease; Down-Regulation; EBNA-1 protein; EBV-associated disease; EBV-associated malignancy; Ensure; Episome; Epitopes; Epstein-Barr Virus Infections; Epstein-Barr Virus latency; Equilibrium; Event; Exons; Foundations; Gene Expression; Gene Expression Regulation; Genetic Transcription; Genome; Growth; Herpesviridae; Homeostasis; Human; Human Herpesvirus 4; Immune; Immune system; Immunologic Surveillance; Individual; Infection; Infectious Mononucleosis; Intervention; Knowledge; Life; Link; Lymphoma; MHC Class I Genes; Maintenance; Malignant Neoplasms; Mediating; Messenger RNA; Molecular; Oncogenic; Pathogenesis; Peptides; Process; Property; Proteins; Publishing; RNA Splicing; Relative (related person); Reporter; Repression; Research; Resistance; Risk; Risk Factors; Role; Screening procedure; Secondary to; Site; T-Lymphocyte; Transcript; Transcription Initiation Site; Viral; Viral Genes; Viral Genome; Viral Proteins; Work; base; cell killing; defined contribution; immune function; infected B cell; insight; latent infection; mRNA Precursor; multicatalytic endopeptidase complex; novel; pathogen; prevent; programs; promoter; public health relevance; research study; response; tumorigenic; viral DNA

DESCRIPTION (provided by applicant): Epstein-Barr virus (EBV) is an extremely successful pathogen, able to persist lifelong as a latent infection within B lymphocytes with little overt disease. However, a breakdown in immune surveillance, e.g., as a consequence of AIDS, remains a significant risk factor for development of EBV-associated lymphoma, underscoring the highly evolved equilibrium that exists between this potentially oncogenic herpesvirus and the host immune system. This equilibrium is dependent on a selective down-regulation of EBV latency-associated gene expression during establishment of persistent infection that ultimately restricts expression to viral genes critical for maintenance of persistence, while precluding those with acute transforming properties and/or which encode dominant epitopes recognized by the EBV-specific T-cell surveillance. A pivotal process in this transition to restricted latency is a promoter switching event that enables exclusive expression of the essential EBV genome-maintenance protein, EBNA-1, from the promoter Qp, which can be negatively autoregulated through two EBNA-1 binding sites immediately downstream of its transcription start site. Our recent efforts to define the mechanism of EBNA-1 repression revealed that it acts not by inhibition of transcription, as originally believed, but by suppression of pre-mRNA processing. The principal significance of this autoregulation, furthermore, has recently become apparent. Although EBNA-1 was earlier thought to be "invisible" to the host immune surveillance as a consequence of its ability to inhibit in cis its degradation by the cell proteasome, thereby preventing presentation of EBNA-1 peptide epitopes in association with HLA class I molecules, subsequent studies indicated that cytotoxic T cells that recognize EBNA-1 not only exist, but that they are directed towards peptides generated during actual synthesis of EBNA-1, not by the degradation of mature EBNA-1. Thus, resistance to proteasomal degradation is secondary to the autoregulated expression of EBNA-1 as the primary mechanism employed by EBV to restrict EBNA-1-specific T-cell killing. Further, recently described anti-apoptotic properties of EBNA-1 suggest that it may have tumorigenic potential. We hypothesize, therefore, that the autoregulatory function of EBNA-1 is highly critical to EBV persistence and its associated pathogenic potential: it ensures sufficient EBNA-1 for genome maintenance, while limiting EBNA-1 synthesis below a threshold that, if exceeded, would subject latently infected B cells to elimination by EBNA-1-specific cytotoxic T cells, and potentially oncogenic transformation. We propose three specific aims to help us reach our long-term objective of defining the contribution of EBNA-1 autoregulation to EBV biology, immune evasion and pathogenesis: 1) Elucidate the influence of EBNA-1 on pre-mRNA processing; 2) Define the molecular mechanism of EBNA-1 autoregulation; and 3) Elucidate the contributions of EBNA-1 autoregulation to the growth and restricted programs of EBV latency. PUBLIC HEALTH RELEVANCE: Epstein-Barr virus (EBV) is a herpesvirus that has significant potential to cause cancer in its human host, particularly within individuals that become immune suppressed as a consequence of AIDS, for example. Through this research we hope to gain a better understanding of how infection by EBV may be prevented or treated. Specifically, we seek to elucidate the mechanism by which a key EBV protein, EBNA-1, regulates its own expression, and to determine the respective importance of this autoregulatory mechanism in the different forms of EBV infection within B lymphocytes. We hypothesize that the autoregulatory function of EBNA-1 ensures that it is expressed at levels necessary to perform its essential role in propagation of the EBV DNA genome, but below levels that would be detected by the host immune system and that might promote malignancy.

描述（由申请人提供）：Epstein-Barr病毒（EBV）是一种非常成功的病原体，能够终身作为B淋巴细胞中的潜在感染，几乎没有明显的疾病。但是，由于艾滋病的结果，免疫监测的细分，例如，由于艾滋病的结果，它仍然是EBV相关淋巴瘤发展的重要危险因素，强调了这种潜在的致癌性疱疹病毒与宿主免疫系统之间存在的高度发展的平衡。这种平衡取决于在建立持久性感染期间与EBV潜伏相关基因表达的选择性下调，最终将表达限制为对维持持久性至关重要的病毒基因，同时排除具有急性转化特性和/或ebv ebv ebv ebv-eptopes的急性转化特性的那些人的表达。在限制潜伏期过渡的过程中，一个关键过程是一个启动子切换事件，该事件可以从启动子QP中获得必需的EBV基因组维持蛋白EBNA-1的独家表达，可以通过两个EBNA-1结合位点对其转录起始位点的下游立即进行负面调节。我们最近定义EBNA-1抑制机制的努力表明，它不是通过抑制转录的作用，而是最初认为的，而是通过抑制MRNA加工的抑制。此外，这种自动调节的主要意义最近已经显而易见。 Although EBNA-1 was earlier thought to be "invisible" to the host immune surveillance as a consequence of its ability to inhibit in cis its degradation by the cell proteasome, thereby preventing presentation of EBNA-1 peptide epitopes in association with HLA class I molecules, subsequent studies indicated that cytotoxic T cells that recognize EBNA-1 not only exist, but that they are directed towards peptides generated during actual EBNA-1的合成，不是通过成熟的EBNA-1的降解。因此，对蛋白酶体降解的耐药性是EBNA-1的自动调节表达为限制EBV限制EBNA-1特异性T细胞杀戮的主要机制的继发性。此外，最近描述的EBNA-1的抗凋亡特性表明它可能具有肿瘤性潜力。 We hypothesize, therefore, that the autoregulatory function of EBNA-1 is highly critical to EBV persistence and its associated pathogenic potential: it ensures sufficient EBNA-1 for genome maintenance, while limiting EBNA-1 synthesis below a threshold that, if exceeded, would subject latently infected B cells to elimination by EBNA-1-specific cytotoxic T cells, and potentially oncogenic transformation.我们提出了三个特定的目的，以帮助我们实现长期目标，以定义EBNA-1自动调节对EBV生物学，免疫逃避和发病机理的贡献：1）阐明EBNA-1对MRNA PRESACTION的影响； 2）定义EBNA-1自动调节的分子机制； 3）阐明EBNA-1自动调节对EBV潜伏期的增长和限制计划的贡献。公共卫生相关性：Epstein-Barr病毒（EBV）是一种疱疹病毒，具有在其人类宿主中引起癌症的巨大潜力，尤其是在因艾滋病而受到免疫抑制的个体中。通过这项研究，我们希望更好地了解如何预防或治疗EBV感染。具体而言，我们试图阐明关键EBV蛋白EBNA-1调节其自身表达的机制，并确定这种自动调节机制在B淋巴细胞中不同形式的EBV感染中的各自重要性。我们假设EBNA-1的自动调节功能可确保其在EBV DNA基因组传播中的重要作用所必需的水平上表达，但是宿主免疫系统将检测到的水平以下，这可能会促进恶性肿瘤。