Role of MED12L- Associated Chromatin Enhancers in Pediatric Acute Megakaryoblastic Leukemia

MED12L 相关染色质增强子在小儿急性巨核细胞白血病中的作用

• 批准号: 10669297
• 负责人: Samrat Roy Choudhury
• 金额: $ 30.24万
• 依托单位: ARKANSAS CHILDREN'S HOSPITAL RES INST
• 依托单位国家: 美国
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-07-11 至 2027-06-30
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10669297
• 关键词: 3 year old; Acute Megakaryocytic Leukemias; Acute Myelocytic Leukemia; Amino Acids; Architecture; Binding; Binding Sites; Bromodomain; CD34 gene; Cell Line; Centers of Research Excellence; Child; Childhood; Childhood Acute Megakaryoblastic Leukemia; Childhood Acute Myeloid Leukemia; Chimeric Proteins; Chromatin; Clustered Regularly Interspaced Short Palindromic Repeats; Development; Disease; Distal; Distant; Doctor of Philosophy; EP300 gene; Elements; Enhancers; Epigenetic Process; Family; GATA1 gene; GLIS2 gene; Gene Expression; Genes; Genetic Enhancer Element; Genetic Transcription; Growth; Histone H3; Human; Impairment; In Vitro; Incidence; Infant; Leukemic Cell; Link; Lysine; Malignant - descriptor; Malignant neoplasm of prostate; Mediating; Mediator; Megakaryocytes; Neoadjuvant Therapy; Oncogenic; Outcome; Pediatric Research; Phosphotransferases; Population; Positioning Attribute; Property; Proteins; RNA Polymerase II; RUNX1 gene; Recurrence; Relapse; Reporting; Research Project Grants; Resources; Role; Somatic Mutation; Squamous cell carcinoma; Survival Rate; Testing; Transcription Coactivator; Umbilical Cord Blood; Zinc Fingers; acute megakaryoblastic leukemia cell; chromatin remodeling; epigenetic regulation; epigenomics; genetic corepressor; genome sequencing; genome-wide; in vivo Model; insight; leukemia; new therapeutic target; novel; novel therapeutic intervention; novel therapeutics; overexpression; paralogous gene; patient population; pre-clinical; progenitor; programs; promoter; proteogenomics; recruit; response; small molecule; stem cells; therapeutic target; transcription factor

Summary The fusion of CBFA2/RUNX1 partner transcriptional co-repressor 3 (CBFA2T3, also known as ETO2) and GLIS family zinc finger 2 (GLIS2) proteins is the most recurrent (30%) alternation in pediatric de novo acute megakaryoblastic leukemia (AMKL). For infants and young children (<3 years of age) harboring ETO2-GLIS2, outcomes are among the worst of all pediatric acute myeloid leukemia (AML) subtypes, with poor responses to induction therapy, high incidence of relapse (~90%), and dismal 5-year survival rates (<20%). Genome sequencing studies have shown the ETO2-GLIS2 fusion and epigenetic regulation to be key drivers of the disease. For instance, transcriptional deregulation in this AML subtype was linked to the cooperative binding of ETO2-GLIS2 to H3K27ac (histone H3, acetyl-lysine amino acid position 27) enriched super-enhancer (SE) chromatin. In leukemic blasts, ETO2-GLIS2 induces formation of unique leukemia-specific SE (neo-SE) elements that would be distantly located from their canonical binding sites in normal megakaryocyte (MK) progenitors. While ETO2-GLIS2 fusion is considered to impact leukemic properties by imbalance of ERG-GATA1 transcription factors (TFs) and enhancer activity in a single oncogenic “hit”, detailed mechanisms by which the fusion protein rearranges chromatin architecture to deregulate transcriptional programs remain elusive. Mediator (MED) proteins are known to assemble transcriptional coactivators distal to the RNA polymerase II binding site to regulate gene expression. Specifically, in leukemic cells, the MED12 subunit or its MK-lineage paralog MED12L of the MED-kinase module was reported to co-recruit regulatory transcription factors (e.g., bromodomain 4, ERG, p300, GATA2) at H3K27ac-enriched SE elements. Moreover, somatic mutations of MED12L or amplifications of chr3q, which harbors the gene, also have been reported as novel oncogenic drivers in squamous cell carcinoma and prostate cancer respectively. MED12L is found overexpressed and controlled by the ETO2-GLIS2 bound SE in this AML subtype. Understanding the role of MED12L in enhancer mechanisms could provide insight into novel treatment approaches. Based on rigorous preliminary studies, we hypothesize that ETO2-GLIS2 exploits focal chromatin features to develop oncogenic neo-SEs, favoring leukemic growth, and that MED12L potentiates formation and transcriptional linkage of these neo-SE elements to induce leukemic gene expression. We will test our hypothesis by pursuing the following specific aims: (1) Determine how ETO2-GLIS2 alters chromatin architecture to facilitate leukemia-specific transcriptional programs and (2) Determine the degree to which MED12L contributes to the global chromatin remodeling and formation of neo-SE.

总结 CBFA 2/RUNX 1伴侣转录共阻遏物3（CBFA 2 T3，也称为ETO 2）和 GLIS家族锌指2（GLIS 2）蛋白是儿童原发性急性白血病中最常见（30%）的变异。 巨核细胞白血病（AMKL）。对于携带ETO 2-GLIS 2的婴幼儿（<3岁）， 结果是所有儿童急性髓细胞白血病（AML）亚型中最差的，对 诱导治疗，复发率高（~90%），5年生存率低（<20%）。基因组 测序研究表明ETO 2-GLIS 2融合和表观遗传调控是基因表达的关键驱动因素。 疾病例如，这种AML亚型中的转录失调与以下因素的协同结合有关： ETO 2-GLIS 2至H3 K27 ac（组蛋白H3，乙酰赖氨酸氨基酸位置27）富集的超级增强子（SE） 染色质在白血病原始细胞中，ETO 2-GLIS 2诱导形成独特的白血病特异性SE（neo-SE） 在正常巨核细胞（MK）中远离其典型结合位点的元件 祖先虽然ETO 2-GLIS 2融合被认为通过ERG-GATA 1失衡影响白血病性质， 转录因子（TF）和增强子活性在一个单一的致癌“击中”，详细的机制， 融合蛋白重排染色质结构以解除转录程序的调控仍然是难以捉摸的。 已知介体（MED）蛋白在RNA聚合酶II的远端组装转录辅激活因子 结合位点来调节基因表达。具体而言，在白血病细胞中，MED 12亚基或其MK谱系 据报道MED-激酶模块的paramedMED 12 L共募集调节转录因子（例如， 溴区结构域4、ERG、p300、GATA 2）在H3 K27 ac富集的SE元件处。此外， MED 12 L或含有该基因的chr 3q的扩增也被报道为新的致癌驱动因子 分别在鳞状细胞癌和前列腺癌中。发现MED 12 L过表达和受控 通过ETO 2-GLIS 2结合的SE。了解MED 12 L在增强子机制中的作用 可以提供新的治疗方法的见解。 基于严格的初步研究，我们假设ETO 2-GLIS 2利用了局灶染色质特征， 发生致癌性新SE，有利于白血病生长，MED 12 L促进形成， 这些neo-SE元件的转录连接诱导白血病基因表达。我们将测试我们的假设 （1）确定ETO 2-GLIS 2如何改变染色质结构， 白血病特异性转录程序和（2）确定MED 12 L对白血病特异性转录程序的贡献程度。 整体染色质重塑和新SE的形成。