Role of Polycomb-mediated epigenetic regulation in diffuse large B cell lymphoma

Polycomb 介导的表观遗传调控在弥漫性大 B 细胞淋巴瘤中的作用

• 批准号: 8258674
• 负责人: ANN J FEENEY
• 金额: $ 33.16万
• 依托单位: SCRIPPS RESEARCH INSTITUTE, THE
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-02-01 至 2014-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8258674
• 关键词: Accounting; Affect; Affinity; Alleles; B cell differentiation; B-Lymphocyte Subsets; B-Lymphocytes; Binding; Biological; Catalytic Domain; Cell Line; ChIP-seq; Complex; DNA; DNA Methylation; Development; Disease; Drosophila genus; Epigenetic Process; Follicular Lymphoma; Frequencies; Gene Expression; Gene Expression Profile; Gene Silencing; Gene Targeting; Genes; Genetic Transcription; Genotype; Histones; Homologous Gene; Human; Lymphoma; Lymphomagenesis; Lysine; Malignant - descriptor; Malignant Neoplasms; Mediating; Memory B-Lymphocyte; Methylation; Methyltransferase; Modification; Molecular Profiling; Molecular Target; Mutate; Mutation; Non-Hodgkin' s Lymphoma; PRC1 Protein; Pathogenesis; Pathway interactions; Pattern; Polycomb; Post-Translational Protein Processing; Proteins; Recruitment Activity; Regulation; Regulator Genes; Repression; Rest; Role; Sampling; Staging; Structure of germinal center of lymph node; Tonsil; Tumor Suppressor Genes; Tumor Suppressor Proteins; Ubiquitination; Ursidae Family; cancer type; cell type; functional group; histone methyltransferase; insight; large cell Diffuse non-Hodgkin' s lymphoma; mutant; neoplastic cell; novel; paralogous gene; uH2A; ubiquitin-protein ligase

DESCRIPTION (provided by applicant): It has become increasingly clear that the pathogenesis of many forms of cancer have a significant epigenetic component. Many cancer types are characterized by gene inactivation, and genes can be silenced through epigenetic mechanisms such as DNA methylation and/or the acquisition of repressive histone 3 modifications such as the methylation of lysines 27 or 9. Methylation of H3K27 is catalyzed by the Polycomb protein Ezh2, the catalytic component of Polycomb Repressive Complex 2 (PRC2). Recently, a specific mutation in the catalytic site of Ezh2 that hyperactivates its H3K27me3 methyltransferase activity while eliminating its ability to monomethylate H3K27 been detected with high frequency in one specific subtype of cancer: the germinal center (GC) B cell subtype of diffuse large B cell lymphoma (GCB-DLBCL). This hyperactive Ezh2 mutation is not present in any other types of lymphomas examined, suggesting that it may be uniquely relevant for GCB- DLBCL lymphomagenesis. Ezh2 transcription is repressed in naove B cells, but it is upregulated in GC B cells. We hypothesize that Ezh2 expression is normally increased at this stage to repress a specific subset of genes that must be downregulated to allow the differentiation of a naove B cell into a GC B cell, and of a GC B cell into a post-GC B cell. Once Ezh2 methylates H3K27, H3K27me3 can be recognized by the Polycomb Repressive Complex 1 (PRC1). The catalytic component of this repressive PRC1 complex is Ring1b, which monoubiquitinates H2A on lysine 119 (uH2A), leading to further repression. However, H2AK119 can be ubiquitinylated by other complexes also. Furthermore, unlike Drosophila PRC1, the basic 4 components in mammalian PRC1 have many alternative paralogs, resulting in a variety of different PRC1 complexes with different affinities for H3K27me3. Very little is known about the biological consequences of PRC1 complexes having different compositions, although it is known that the 4 mammalian paralogs of the histone binding subunit have varying affinities for H3K27me3. We hypothesize that a direct downstream consequence of more H3K27me3 in a subset of GCB-DLBCL may be that there will be more PCR1 recruitment and/or recruitment of different PRC1 complexes. This could result in more uH2A and/or more DNA methylation on some genes. Consequently, these genes are likely to display the most dysregulation. This project will characterize the Polycomb-mediated epigenetic changes that take place in normal human B cells as they differentiate into GC B cells, then into post-GC memory B cells. We will perform ChIP-seq to identify PRC1 components binding to H3K27me3, and compare this to the expression profile and DNA methylation profile to determine which genes are normally repressed in a Polycomb-mediated manner. We will analyze a large set of GC-DLBCL, will determine the epigenetic profile of lymphomas that bear or do not bear the Ezh2 mutation, and will relate this to their gene expression profile. These studies will provide insight into the dysregulation of genes in GCB- DLBCL, and will also provide novel information on the normal epigenetic mechanisms by which genes are repressed in a Polycomb-dependent manner during the late steps of B lymphocyte differentiation. PUBLIC HEALTH RELEVANCE: Diffuse large B cell lymphoma (DLBCL) is an aggressive disease that accounts for 40% of all non- Hodgkins lymphomas, and the GCB subset has been described to have a unique mutation in the histone methyltransferase, Ezh2. Finding genes that are specifically misregulated due to the Ezh2 mutation, and understanding the downstream consequences of bearing this mutant Ezh2, will be a major step forward in pinpointing key molecular targets that may be involved in the pathogenesis of GCB-DLBCL. The novel information we will gain regarding the various mechanisms of Polycomb- mediated repression in normal germinal center B cells, the cell type that undergoes the malignant transformation to GCB-DLBCL, will be essential to understand the misregulation that occurs in lymphomagenesis.

描述（由申请人提供）：越来越清楚的是，许多形式的癌症的发病机理具有显着的表观遗传成分。许多癌症类型的特征是基因失活的特征，可以通过表观遗传机制（例如DNA甲基化和/或获得抑制性组蛋白3修饰）（例如赖氨酸27或9的甲基化）进行沉默。最近，EZH2催化位点的特异性突变超过其H3K27ME3甲基转移酶活性，同时消除了其在一个特定的癌症的一个特定亚型中以高频率检测到其单甲基盐H3K27的能力：生发性中心（GC）B细胞B细胞Belly Blige B细胞子型（GC）B细胞子型（GC）大细胞lympphoma of Diffuse ligh Bellypepe（GC）。在检查的任何其他类型的淋巴瘤中，这种多动过的EZH2突变都不存在，这表明它可能与GCB-DLBCL淋巴细胞促性异常相关。 EZH2转录在NAOVE B细胞中受到抑制，但在GC B细胞中被上调。我们假设在此阶段，EZH2表达通常会增加，以抑制必须下调的特定基因子集，以使NaOVE B细胞分化为GC B细胞，而GC B细胞将NaOVE B细胞分化为GC B细胞中的GC B细胞。一旦EZH2甲基化H3K27，H3K27me3就可以通过Polycomb抑制复合物1（PRC1）识别。这种抑制性PRC1复合物的催化成分是RING1B，它在赖氨酸119（UH2A）上单喹啉量产生了单喹，导致进一步的抑制作用。但是，H2AK119也可以被其他复合物泛素化。此外，与果蝇PRC1不同，哺乳动物PRC1中的基本4个成分具有许多替代旁系同源物，从而产生了各种不同的PRC1配合物，对H3K27Me3具有不同的亲和力。对于具有不同组成的PRC1复合物的生物学后果知之甚少，尽管众所周知，组蛋白结合亚基的4个哺乳动物旁系同源物对H3K27me3具有不同的亲和力。我们假设在GCB-DLBCL子集中，更多H3K27me3的直接下游结果可能是，PCR1募集和/或募集了不同的PRC1复合物。这可能会导致某些基因上更多的UH2A和/或更多的DNA甲基化。因此，这些基因可能显示出最大的失调。该项目将表征PolyComb介导的表观遗传学变化，它们在正常的人类B细胞中分化为GC B细胞，然后分解为GC后记忆B细胞。我们将执行CHIP-SEQ，以识别与H3K27me3结合的PRC1成分，并将其与表达曲线和DNA甲基化谱进行比较，以确定通常以多孔介导的方式抑制哪些基因。我们将分析一大批GC-DLBCL，将确定伴有或不承受EZH2突变的淋巴瘤的表观遗传谱，并将其与其基因表达谱有关。这些研究将提供有关GCB-DLBCL基因失调的洞察力，还将提供有关正常表观遗传机制的新信息，在B淋巴细胞分化的后期，以多肉液依赖性方式抑制基因。 公共卫生相关性：弥漫性大B细胞淋巴瘤（DLBCL）是一种侵略性疾病，占所有非Hodgkins淋巴瘤的40％，GCB子集已被描述为在组蛋白甲基转移酶EZH2中具有独特的突变。在发现该突变体EZH2的下游后果以及了解可能与GCB-DLBCL发病机理有关的关键分子靶标方面，找到了由于EZH2突变而被特异性误导的基因，并了解了轴承EZH2的下游后果。我们将获得有关正常生发中心B细胞中多型介导的抑制的各种机制的新信息，这是经历恶性转化向GCB-DLBCL的细胞类型，对于了解淋巴结作中发生的错误调节至关重要。