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

基本信息

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
项目类别：
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

项目摘要

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.

项目概要逆转录转座子在人类癌症中的作用历来被低估，因为它们被认为是不重要的“垃圾”DNA，并且因为它们的高重复性和变异性造成了显着的影响技术挑战 LINE-1（或 L1）反转录转座子有约 500,000 个拷贝，占 17%。人类基因组，但只有约 100 个全长人类特异性 L1 元件 (L1H) 能够激活 L1 编码的蛋白质还动员非自主逆转录转座子、非编码 RNA 和 mRNA，导致三分之一的人类 DNA 的产生，因此，L1 被认为是主要的。有害，因为它们的活性可能导致基因突变和染色体改变，从而导致通过对人类染色质调节因子进行基于域的 CRISPR 筛选，我们发现了包括癌症在内的人类疾病。 MPP8 是 HUSH 复合体的一个组成部分，负责 L1 反转录转座子的沉默，急性髓性白血病（AML）细胞的选择性表观遗传依赖性，而对于正常细胞来说是可有可无的。造血过程中，MPP8 缺失会通过重新激活 L1 异位激活来损害 AML 的启动和维持。表型复制 MPP8 丢失，而阻断 L1 逆转座则消除了 L1 抑制。因此，逆转录转座子与人类 AML 患者的治疗耐药性和不良预后相关。历史上人们认为它们具有促进癌症的作用，是遗传不稳定和体细胞的来源突变，我们的研究结果支持逆转录转座子作为一种选择性抑制剂具有意想不到的“肿瘤抑制”功能该项目的目标是阐明髓系白血病的功能和机制作用。 L1 逆转录转座子作为 AML 病理生理学的新调控途径中心假设是 L1。反转录转座子在 AML 起始过程中调节 DNA 损伤反应和/或炎症信号传导细胞，L1 活性控制着髓系白血病中 DNA 损伤诱导剂的治疗反应。我们的假设是在使用正交法进行广泛初步研究的基础上制定的在生理相关的 AML 模型中调节 L1 功能的方法和新发现的分子逆转录转座子的抑制与癌症起始细胞的增殖之间的联系。根据研究结果，这些假设将通过三个具体目标进行检验：1）建立 L1 的功能角色逆转录转座子在髓系白血病克隆进化中的作用2)阐明L1的机制作用。逆转录转座子在 AML 发病机制中的作用 3) 确定调节逆转录转座子活性对细胞的影响。综上所述，这些研究将探讨髓系白血病中 DNA 损伤诱导剂的治疗反应。不仅阐明了逆转录转座子意想不到的“肿瘤抑制”功能的机制基础髓性白血病的活性，而且还为移动 DNA 元件建立了一个新的范式，作为以前的研究白血病生物学中未知的调控途径，其干预可能会改善抗白血病效果疗法。