Functions and mechanisms of transcriptional coactivator OCA-B in B cell development and lymphomagenesis

转录共激活因子 OCA-B 在 B 细胞发育和淋巴瘤发生中的功能和机制

• 批准号: 10303052
• 负责人: ROBERT G ROEDER
• 金额: $ 73.75万
• 依托单位: ROCKEFELLER UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-12-12 至 2024-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10303052
• 关键词: Adaptive Immune System; Address; Affinity; Anatomy; Antibodies; Antigens; Autoimmune Diseases; Autoimmunity; B cell differentiation; B-Cell Development; B-Cell Lymphomas; B-Lymphocytes; BCL6 gene; Binding; Biochemical; Bioinformatics; Biological Assay; Burkitt Lymphoma; C-terminal; Cell Culture System; Cell Line; Cell Maturation; Cell Proliferation; Cells; Chromatin; Clonal Expansion; Complex; DNA; Data; Defect; Dependence; Development; Disease; Distal; Drug Targeting; Enhancers; Epigenetic Process; Gene Activation; Genes; Genetic; Genetic Transcription; Genomic approach; Genomics; Goals; Health; Hematopoietic stem cells; Human; Immune; Immune response; Immune system; Immunoglobulin Genes; Immunoglobulin Somatic Hypermutation; Immunoglobulin-Secreting Cells; Immunotherapy; Impairment; In Vitro; Knockout Mice; Lead; Locus Control Region; Lymphoid; Lymphoma; Lymphoma cell; Lymphomagenesis; Malignant Neoplasms; Mediating; Mediator of activation protein; Memory B-Lymphocyte; Molecular Mechanisms of Action; Mutation; Oncogenic; POU2F1 gene; Pathway interactions; Play; Process; Proteomics; Recombinants; Recurrence; Reporter; Reporting; Response Elements; Role; Series; Signal Pathway; Site; Structure; Structure of germinal center of lymph node; System; Time; Transcription Coactivator; Transcriptional Regulation; base; cell growth; cofactor; gene regulatory network; genetic approach; imaging approach; in vivo; insight; large cell Diffuse non-Hodgkin' s lymphoma; mouse model; neoplastic cell; novel therapeutic intervention; programs; promoter; reconstitution; recruit; response; secondary lymphoid organ; transcription factor

PROJECT SUMMARY A functional immune system is central to human health and, at the same time, alterations of normal lymphoid developmental programs can lead to immune deficiencies, autoimmune diseases and a variety of lymphomas. Germinal centers (GCs) are microanatomical structures formed in secondary lymphoid organs during antigen- stimulated immune responses. GCs are the sites of B cell maturation through clonal expansion, somatic hypermutation, and affinity-mediated selection -- and therefore play a critical role in differentiation of antibody secreting cells and memory B cells. OCA-B is a unique transcriptional coactivator that is highly expressed in GC B cells and GC-derived lymphomas such as diffuse large B cell lymphoma and Burkitt’s lymphoma. In vivo studies have demonstrated that OCA-B is essential for both antigen-dependent B cell differentiation (including GC formation) and normal expression of secondary immunoglobulin genes. However, little is known about the exact role of OCA-B in normal GC formation and GC-derived lymphoma progression. In addition, the mechanism by which OCA-B regulates its target genes is also unclear. In addressing these issues, our preliminary studies have demonstrated (i) a functional occupancy of OCA-B on distal enhancers, in particular the large locus control region (LCR) of the BCL6 gene that encodes a master regulator of GC formation; (ii) direct interactions of OCA- B with the MED1 subunit of the Mediator coactivator complex and with a GC-specific transcription factor (MEF2B) important for BCL6 expression and (iii) a B cell-intrinsic Oca-B dependency for GC B cell differentiation in vivo. Based on our previous OCA-B studies and recent preliminary data, we hypothesize that a predominant role of OCA-B in GC formation involves activation of BCL6 through its distal enhancer region by recruiting and concentrating transcription factors and cofactors, including chromatin/epigenetic factors, that facilitate enhancer- promoter interactions. We also hypothesis that OCA-B plays a critical role in GC-derived lymphomagenesis. To address these issues, we will investigate (i) the function and mechanism of action of OCA-B, through interactions with MED1/Mediator and MEF2B, on the BCL6 LCR/super-enhancer in both ex vivo GC B and lymphoma cells, (ii) the mechanism of action of OCA-B-dependent transcriptional coactivation through rigorous biochemical in vitro transcription assays; (iii) the mechanism of action of OCA-B in GC B cell differentiation in vivo, including identification of key target genes and regulatory networks; (iv) the role of OCA-B in B cell lymphoma progression in vivo. We will use complementary biochemical, genomic, bioinformatic, genetic, gene-editing, cell-based and in vivo (mouse model) approaches. Completion of these aims will advance our understanding of the molecular mechanism of action of OCA-B in GC-specific transcriptional regulation, GC B cell differentiation, and GC- derived B cell lymphomagenesis. Notably, it also will provide clues to new therapeutic strategies for treating B cell lymphomas.

项目概要 功能性免疫系统对于人类健康至关重要，同时也影响正常淋巴系统的改变 发育计划可能导致免疫缺陷、自身免疫性疾病和各种淋巴瘤。 生发中心（GC）是在抗原-免疫过程中在次级淋巴器官中形成的显微​​解剖结构。 GC 是 B 细胞通过克隆扩增、体细胞成熟的场所。 超突变和亲和力介导的选择——因此在抗体的分化中发挥着关键作用 OCA-B 是一种独特的转录共激活因子，在 GC 中高度表达。 B 细胞和 GC 衍生的淋巴瘤，例如弥漫性大 B 细胞淋巴瘤和伯基特淋巴瘤体内。 研究表明 OCA-B 对于抗原依赖性 B 细胞分化（包括 GC 形成）和次级免疫球蛋白基因的正常表达然而，人们对此知之甚少。 OCA-B 在正常 GC 形成和 GC 衍生淋巴瘤进展中的确切作用。 OCA-B通过何种方式调节其靶基因也不清楚。在解决这些问题时，我们的初步研究还不清楚。 已经证明 (i) OCA-B 对远端增强子的功能占据，特别是大基因座控制 BCL6 基因的区域 (LCR) 编码 GC 形成的主调节因子；(ii) OCA-的直接相互作用； B 具有介体共激活复合物的 MED1 亚基和 GC 特异性转录因子 (MEF2B) 对于 BCL6 表达很重要，并且 (iii) B 细胞固有的 Oca-B 依赖性对于体内 GC B 细胞分化很重要。 根据我们之前的 OCA-B 研究和最近的初步数据，我们追求主导作用 OCA-B 在 GC 形成中的作用涉及通过其远端增强子区域招募和激活 BCL6 集中转录因子和辅助因子，包括染色质/表观遗传因子，促进增强子- 我们还假设 OCA-B 在 GC 衍生的淋巴瘤发生中发挥着关键作用。 为了解决这些问题，我们将通过相互作用研究（i）OCA-B的功能和作用机制 与 MED1/Mediator 和 MEF2B 一起，在离体 GC B 和淋巴瘤细胞中的 BCL6 LCR/超级增强子上， (ii) OCA-B依赖性转录共激活通过严格的生物化学作用机制 体外转录测定；(iii) OCA-B 在体内 GC B 细胞分化中的作用机制，包括 确定关键靶基因和调控网络；(iv) OCA-B 在 B 细胞淋巴瘤进展中的作用； 我们将使用互补的生化、基因组、生物信息学、遗传学、基因编辑、基于细胞和 体内（小鼠模型）方法的完成将增进我们对分子的理解。 OCA-B 在 GC 特异性转录调控、GC B 细胞分化和 GC- 中的作用机制 值得注意的是，它也将为治疗 B 细胞淋巴瘤的新治疗策略提供线索。 细胞淋巴瘤。