EBNA1 Functions Required in Burkitt's Lymphomas and Other Immortalized B-Cells

伯基特淋巴瘤和其他永生化 B 细胞所需的 EBNA1 功能

• 批准号: 8117481
• 负责人: Amber Teresa Keizerweerd
• 金额: $ 2.94万
• 依托单位: LSU HEALTH SCIENCES CENTER
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-07-01 至 2013-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8117481
• 关键词: AIDS Related Immunoblastic Lymphoma; AT-Hook Motifs; Affect; Apoptosis; B Cell Proliferation; B-Cell Lymphomas; B-Lymphocytes; Binding; Burkitt Lymphoma; Carcinoma; Cell Line; Cell Proliferation; Cell physiology; Cells; Communicable Diseases; Cysteine; DNA; Diagnosis; Disease; Dominant-Negative Mutation; EBNA2 protein; EBV-associated disease; Ectopic Expression; Epstein-Barr Virus Infections; Gene Expression; Genes; Genetic Transcription; Genome Stability; Goals; Growth; Health; Herpesviridae; Human; Human Herpesvirus 4; In Vitro; Individual; LMP1; Lymphoma; Lymphoproliferative Disorders; Malignant - descriptor; Malignant Neoplasms; Nasopharynx Carcinoma; Nuclear; Nuclear Antigens; Oncogenic; Oxidation-Reduction; Oxidative Stress; Pattern; Publishing; RNA Interference; Reactive Oxygen Species; Reporting; Research; Resistance; Role; Social Welfare; Stomach Carcinoma; Testing; Therapeutic; Trans-Activators; Transactivation; Transplantation; Viral Genes; Viral Proteins; Virus; Woman; Zinc; base; cancer statistics; cytochrome b245; gene replacement; infected B cell; inhibitor/antagonist; lymphoblastoid cell line; men; mutant; new therapeutic target; peptidomimetics; therapeutic target

Epstein-Barr Virus (EBV) is an oncogenic human herpesvirus predominantly infecting B-lymphocytes that is etiologically associated with Burkitt's lymphoma, AIDS-related immunoblastic lymphomas, post- transplant lymphoproliferative disease, nasopharyngeal carcinoma, and gastric carcinoma. Very few viral genes are expressed in these malignancies and diseases, and infectious virus is almost never released. Therefore, this type of EBV infection is called latency. There are three patterns of viral gene expression observed during latency, termed Type I, Type II and Type III. A nuclear EBV protein called the Epstein-Barr nuclear antigen 1 (EBNA1) is expressed during all three types of latency, but its function differs between latency types. In Type II and Type III latency, EBNA1 activates transcription of other viral genes required for cell proliferation, such as LMP1 and EBNA2. Type II latency is usually observed in EBV-associated carcinomas, whereas Type III latency is observed in AIDS-related immunoblastic lymphomas, post-transplant lymphoproliferative disease, and when EBV immortalizes naive B-cells in vitro. EBNA1 does not transactivate viral genes during Type I latency, which is observed in malignancies such as Burkitt's lymphomas. However, in such cells, EBNA1 has been reported to transactivate the expression of cellular genes. In addition, expression of a dominant-negative EBNA1 that cannot activate transcription severely reduces the aggressive proliferation of EBV-positive Burkitt's lymphoma cells, and induces apoptosis in the majority of cells. Surprisingly, in contrast to these results, over-expression of EBNA1 inhibits the growth of EBV-negative Burkitt's lymphoma cells. Therefore, the ability of EBNA1 to transactivate has contrasting effects on the growth and survival of EBV-positive and EBV-negative Burkitt's lymphomas. A study published recently demonstrates that EBNA1 induces reactive oxygen species (ROS) when expressed in Burkitt's lymphomas, and thereby negatively affects genomic stability. EBNA1 generates ROS by increasing the expression of cytochrome b-245 heavy chain (NOX2). Recent studies on the transactivation mechanism of EBNA1 have shown that EBNA1 needs three domains to transactivate: a) two domains that bind AT-rich DNA, and are termed AT-hooks; and b) a domain called unique region 1 (UR1) that contains an essential conserved cys-x-x-cys motif that permits EBNA1 to dimerize by coordinating zinc. The two cysteines in UR1 are regulated by oxidative stress (redox), such that under oxidative conditions, EBNA1 does not transactivate viral genes. These conditions also interfere with the proliferation of B-cells transformed by EBV in vitro. I propose investigating the functions and domains of EBNA1 required for proliferation of EBV-immortalized lymphoblastoid cell lines, and EBNA1 functions necessary for the aggressive proliferation of malignant Burkitt's lymphoma cells. My studies will identify new therapeutic targets against diseases and malignancies caused by latent EBV infections.

EB病毒(Epstein-Barr Virus，EBV)是一种致癌性人类疱疹病毒，主要感染B淋巴细胞，与Burkitt淋巴瘤、艾滋病相关免疫母细胞淋巴瘤、移植后淋巴增生性疾病、鼻咽癌和胃癌有关。在这些恶性肿瘤和疾病中表达的病毒基因很少，传染性病毒几乎永远不会释放。因此，这种类型的EBV感染称为潜伏期。在潜伏期有三种病毒基因表达模式，称为I型、II型和III型。一种名为Epstein-Barr核抗原1(EBNA1)的核EBV蛋白在所有三种潜伏期都有表达，但其功能因潜伏期类型而异。在II型和III型潜伏期，EBNA1激活细胞增殖所需的其他病毒基因的转录，如LMP1和EBNA2。II型潜伏期通常见于EBV相关癌，而III型潜伏期则见于艾滋病相关免疫母细胞性淋巴瘤、移植后淋巴增生性疾病以及EBV在体外使原始B细胞永生化。EBNA1在I型潜伏期不会反式激活病毒基因，这种潜伏期在Burkitt淋巴瘤等恶性肿瘤中可以观察到。然而，据报道，在这类细胞中，EBNA1可以反式激活细胞基因的表达。此外，不能激活转录的显性负性EBNA1的表达严重降低了EBV阳性的Burkitt淋巴瘤细胞的侵袭性增殖，并诱导了大多数细胞的凋亡。令人惊讶的是，与这些结果相反，EBNA1的过度表达抑制了EBV阴性的Burkitt淋巴瘤细胞的生长。因此，EBNA1的反式激活能力对EBV阳性和EBV阴性的Burkitt淋巴瘤的生长和生存有着截然不同的影响。最近发表的一项研究表明，EBNA1在Burkitt淋巴瘤中表达时会诱导活性氧物种(ROS)，从而对基因组稳定性产生负面影响。EBNA1通过增加细胞色素b-245重链(NOX2)的表达来产生ROS。最近对EBNA1反式激活机制的研究表明，EBNA1需要三个结构域来反式激活：a)两个结构域，结合富含AT的DNA，被称为AT-挂钩；b)一个称为唯一区域1(UR1)的结构域，它包含一个基本保守的cys-x-x-cys基序，允许EBNA1通过配位锌而二聚化。UR1中的两个半胱氨酸受氧化应激(氧化还原)的调节，因此在氧化条件下，EBNA1不能反式激活病毒基因。这些条件也干扰了EB病毒转化的B细胞在体外的增殖。我建议研究EBV永生化的淋巴母细胞系增殖所需的EBNA1的功能和结构域，以及EBNA1对恶性Burkitt淋巴瘤细胞侵袭性增殖所必需的功能。我的研究将确定针对潜伏的EBV感染引起的疾病和恶性肿瘤的新治疗靶点。