Elucidating the Functional and Mechanistic Roles of LINE-1 Retrotransposons in Myeloid Leukemia

阐明 LINE-1 逆转录转座子在髓系白血病中的功能和机制作用

• 批准号: 10860830
• 负责人: Jian Xu
• 金额: $ 47.98万
• 依托单位: ST. JUDE CHILDREN'S RESEARCH HOSPITAL
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-12-01 至 2026-11-30
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10860830
• 关键词: Acute Myelocytic Leukemia; Affect; Biology; CRISPR interference; CRISPR screen; CRISPR-mediated transcriptional activation; Cell Cycle; Cells; Chemoresistance; Chromatin; Chromosome abnormality; Clonal Evolution; Complex; DNA; DNA Damage; DNA Sequence Alteration; DNA Transposable Elements; Dependence; Development; Disease; Elements; Epigenetic Process; Functional disorder; Generations; Genetic; Genomic Instability; Genomics; Goals; Hematopoiesis; Hematopoietic stem cells; Human; Human Genome; Impairment; In Vitro; Inflammatory; Insertional Mutagenesis; Interferon Type I; Intervention; Junk DNA; L1 Elements; Length; Link; Long Interspersed Elements; Maintenance; Malignant - descriptor; Malignant Neoplasms; Mediating; Messenger RNA; Modeling; Molecular; Mus; Myelogenous; Myeloid Leukemia; Oncogenes; Pathogenesis; Pathway interactions; Patients; Phenocopy; Phenotype; Physiological; Prognosis; Prognostic Marker; Proteins; Regulatory Pathway; Repression; Resistance; Retrotransposition; Retrotransposon; Role; Signal Pathway; Signal Transduction; Somatic Mutation; Source; Testing; Therapeutic; Transgenic Organisms; Untranslated RNA; Variant; Work; Xenograft procedure; acute myeloid leukemia cell; antileukemic agent; cancer initiation; epigenetic regulation; epigenetic silencing; genome integrity; high risk; human DNA; improved; in vivo; innovation; leukemia; leukemia initiating cell; leukemia treatment; leukemogenesis; mouse model; overexpression; pharmacologic; response; self-renewal; targeted treatment; transposon/insertion element; treatment response; tumor

PROJECT SUMMARY The role of retrotransposons in human cancer has been historically underappreciated both because they have been dismissed as unimportant ‘junk’ DNA, and because their high repetition and variation pose significant technical challenges. There are ~500,000 copies of LINE-1 (or L1) retrotransposons occupying 17% of the human genome, but only ~100 full-length human-specific L1 elements (L1Hs) are capable of active retrotransposition. L1-encoded proteins also mobilize non-autonomous retrotransposons, noncoding RNAs and mRNAs, leading to the generation of a third of human DNA. As such, L1s have been considered mostly deleterious because their activity can lead to genetic mutations and chromosomal alterations that contribute to human disorders including cancer. By domain-based CRISPR screens of human chromatin regulators, we identified MPP8, a component of the HUSH complex responsible for the silencing of L1 retrotransposons, as a selective epigenetic dependency of acute myeloid leukemia (AML) cells. While dispensable for normal hematopoiesis, MPP8 loss impaired AML initiation and maintenance by reactivating L1s. Ectopic L1 activation phenocopied MPP8 loss, whereas blocking L1 retrotransposition abrogated the phenotypes. L1 suppression is associated with therapy resistance and poor prognosis in human AML patients. Hence, while retrotransposons are historically recognized for their cancer-promoting roles as sources of genetic instability and somatic mutations, our findings support an unexpected ‘tumor-suppressive’ function for retrotransposons as a selective dependency for myeloid leukemia. The goal of this project is to elucidate the functional and mechanistic roles of L1 retrotransposons as a new regulatory pathway in AML pathophysiology. The central hypotheses are that L1 retrotransposons function to modulate DNA damage response and/or inflammatory signaling in AML-initiating cells, and that L1 activity controls therapeutic response to DNA damage-inducing agents in myeloid leukemia. Our hypotheses have been formulated on the basis of extensive preliminary studies using orthogonal approaches to modulate L1 function in physiologically relevant AML models and a newly discovered molecular link between suppression of retrotransposons and propagation of cancer-initiating cells. Guided by these findings, these hypotheses will be tested by three specific aims: 1) Establish the functional roles of L1 retrotransposons in the clonal evolution of myeloid leukemia. 2) Elucidate the mechanistic roles of L1 retrotransposons in AML pathogenesis. 3) Determine the effects of modulating retrotransposon activity on therapeutic response to DNA damage-inducing agents in myeloid leukemia. Taken together, these studies will not only elucidate the mechanistic basis for the unexpected ‘tumor-suppressive’ function for retrotransposon activity in myeloid leukemia, but also establish a new paradigm for mobile DNA elements as a previously uncharted regulatory pathway in leukemia biology, whose intervention may lead to improved anti-leukemia therapies.

项目摘要 从历史上看 我们被视为不重要的“垃圾” DNA，因为它们的高度重复和变化显着 技术挑战。有约500,000份Line-1（或L1）逆转座子，占17％的副本 人类基因组，但只有〜100个全长人类特异性L1元素（L1HS）能够活跃 逆转录。 L1编码的蛋白还动员非自治逆转录子，非编码RNA和 mRNA，导致三分之一的人DNA产生。因此，L1被认为主要是 有害，因为它们的活性会导致基因突变和染色体改变，这有助于 包括癌症在内的人类疾病。通过基于域的CRISPR屏幕人类染色质调节剂，我们 确定的MPP8是负责L1逆转座子沉默的静静综合体的一个组成部分 急性髓样白血病（AML）细胞的选择性表观遗传依赖性。虽然适合正常 造血，MPP8损失通过重新激活L1S损害AML倡议和维持。异位L1激活 表型MPP8损失，而阻塞L1逆转录置位废除了表型。 L1抑制是 与人类AML患者的耐药性和预后不良相关。因此，在逆转座子中 历史上以促进癌症的角色作为遗传不稳定性和躯体的来源而受到认可 突变，我们的发现支持逆转座子作为选择性的意外的“肿瘤抑制”功能 髓样白血病的依赖性。该项目的目的是阐明 L1逆转座子作为AML病理生理学的新调节途径。中心假设是L1 逆转录座子功能可在AML发射中调节DNA损伤响应和/或炎症信号传导 细胞，L1活性控制对髓样白血病中DNA损伤剂的热反应。 我们的假设是根据使用正交的广泛初步研究提出的 在物理相关的AML模型和新发现的分子中调节L1功能的方法 抑制逆转座子的抑制与癌性细胞的传播之间的联系。由这些指导 调查结果，这些假设将通过三个特定目的测试：1）确定L1的功能作用 髓样白血病的克隆进化中的逆转座子。 2）阐明L1的机械作用 AML发病机理中的逆转录子。 3）确定调节逆转座子活性对 对髓样白血病中DNA损伤剂的治疗反应。两者一起，这些研究将 不仅阐明了逆转录子的意外“肿瘤抑制”功能的机械基础 髓样白血病的活动，但也为移动DNA元素建立了新的范式 白血病生物学的未知监管途径，其干预可能会改善抗白血病 疗法。