Role of HOTTIP/beta-catenin-HOXA9/PRMT1 axis in hematopoietic and leukemic stem cells

摘要： 自我更新是一种不可或缺的特性，它允许干细胞再生并维持细胞内环境的稳态。 功能多样的细胞群。造血干细胞（HSC）自我更新的失调直接与 涉及许多造血退化性疾病包括骨髓衰竭和各种血液疾病， 而其异常激活是白血病干细胞（LSC）的定义和不可或缺的特征， 恶性表型我们和其他人已经表明，急性髓细胞白血病（AML）干细胞的自我更新 细胞严重依赖经典Wnt信号通路的关键组分β-连环蛋白和同源框蛋白， H0XA 9在很大程度上是成体HSC的标志物。虽然这些发现揭示了一个对比功能 AML的潜在治疗机会，开发小分子抑制剂， 到目前为止，致癌转录因子的研究很少成功，这主要是因为我们缺乏对 关于这些蛋白质在介导造血自我更新中的分子调控， 这阻碍了在开发有效的治疗策略以治疗由此产生的疾病方面取得进展。有趣的是，我们 最近揭示了经典Wnt通路和后HOXA位点（包括HOXA 9）的共调节 长链非编码RNA（lncRNA），HOTTIP。引人注目的是，我们还报告了一种新的β-连环蛋白之间的串扰 和HOXA 9，其可以在HSC起源的小鼠和人AML中超越它们的个体需求。在 为了寻找β-catenin和Hoxa9功能的关键介质，我们进一步确定了蛋白精氨酸 甲基转移酶1（PRMT1），也涉及DNA损伤和修复（DDR），可以在功能上取代 AML干细胞中的HOXA 9或β-catenin来源于HSC。PRMT 1与DDR复合物无偏 与CTCF/粘附素复合物、造血转录因子（TF）和核小体一起分离沿着 通过ChIRP-MS在AML细胞中将重塑因子作为HOTTIP相互作用伴侣。这些发现不仅揭示了 一种新的HOTTIP/β-catenin-HOXA 9/PRMT 1轴对介导造血自我更新至关重要，但也导致 HOTTIP/β-catenin-HOXA 9/PRMT 1轴协调造血自我更新的中心假设， 各个元件的功能特性及其沿轴沿着的串扰调节 造血特异性转录网络和DDR途径调节造血自我更新 疾病设置。在这个建议中，我们将1破译HOTTIP和造血TF的协同作用， β-catenin轴的调控; 2）分析β-catenin轴的分子功能和调控。 H0XA 9/Prmt 1轴在正常和恶性造血中的作用成功完成拟议的研究， 这不仅将建立分子原理，而且还有助于设计特定的治疗方法， 正常和恶性干细胞的自我更新活动，这可能会转化为患者 效益

Abstract: Self-renewal is an indispensable property that allows stem cells to regenerate and maintain the homeostasis of functionally diverse cell populations. Dergulation of self-renewal in hematopoietic stem cell (HSC) directly links to a number of hematopoietic degenerative disorders including bone marrow failure and various blood diseases, whereas its aberrant activation is a defining and indispensable feature of leukemia stem cells (LSCs) that sustain the malignant phenotypes. We and others have shown that self-renewal of acute myeloid leukemia (AML) stem cells heavily rely on the key component of canonical Wnt signaling pathway, β-catenin and the homeobox protein, HOXA9 that are largely dispensable for adult HSCs. Although these findings reveal a contrasting functional requirement and a potential therapeutic opportunity for AML, development of small molecule inhibitors against oncogenic transcription factors has so far met with very little success largely due to our lack of understanding about the molecular regulations of these proteins in mediating hematopoietic self-renewal, which has significantly hindered progress in developing effective therapeutic strategies to treat the resultant diseases. Intriguingly, we have recently revealed coregulation of both canonical Wnt pathway and posterior HOXA loci including HOXA9 by the long non-coding RNA (lncRNA), HOTTIP. Strikingly, we also report a novel crosstalk between β-catenin and HOXA9 that can override their individual requirement in both mouse and human AML of HSC origins. In search for crucial mediators for β-catenin and Hoxa9 functions, we further identified that protein arginine methyltransferase 1 (PRMT1), which also implicates in DNA damage and repair (DDR), can functionally replace HOXA9 or β-catenin in AML stem cell originated from HSCs. PRMT1 together with DDR complex are unbiasedly isolated along with CTCF/cohesin complex, hematopoietic transcription factors (TFs) and nucleosome remodeling factors as HOTTIP interacting partners by ChIRP-MS in AML cells. These findings not only discover a novel HOTTIP/β-catenin-HOXA9/PRMT1 axis critical for mediating hematopoietic self-renewal, but also lead to central hypothesis that HOTTIP/β-catenin-HOXA9/PRMT1 axis coordinates hematopoietic self-renewal and characterization of the functions of individual components and their crosstalk along the axis regulates hematopoietic specific transcription networks and DDR pathways to modulate hematopoietic self-renewal in the disease setting. In this proposal, we will 1 decipher cooperative action of HOTTIP and hematopoietic TFs in regulating HOXA9 and β-catenin axis; 2) dissect the molecular functions and regulation of β-catenin- HOXA9/Prmt1 axis during normal and malignant hematopoiesis. Success completion of proposed studies not only will establish the molecular principles, but also facilitate the design of specific therapeutics in modulating self-renewal activities in normal and malignant stem cells, which can be potentially translated into patient benefits.