mRNA stability and its impact on hematopoiesis and acute leukemia

摘要 该应用程序的重点是急性髓细胞白血病（AML），一种血液癌症，其特征是低分化。 存活率和可用的靶向治疗很少。AML的五年总生存率低于 成年人为30%，儿童约为65%。有趣的是，一种类型的干预， 对AML（急性早幼粒细胞白血病，APL）亚型成功的是“分化”疗法， 其中药物可以诱导肿瘤细胞分化和凋亡。在这里我们展示表面抗原- 在AML中进行CRISPR/CAS9分化筛选，并研究这些研究中最突出的命中之一。 筛选RNA结合蛋白（RBP）ZFP 36 L2。RBP可以在多个水平上修饰RNA，包括 拼接、加工、修饰和降解。考虑到RBP是基因的关键调节因子， 表达，这些蛋白质的改变也涉及几种人类遗传疾病， 包括癌症我们的实验室最近提出了CRISPR/CAS9筛选RBP在几个 类型的人类白血病和血液癌症中剪接体机制的新调节剂。 我们的CRISPR筛选鉴定了ZFP 36 L2，其为TIS 11/TTP锌指蛋白家族的成员。 RBP还包括ZFP 36和ZFP 36 L1旁系同源物。我们能够证明ZFP 36 L2结合 许多mRNA的3'非翻译区（UTR）上富含AU的元件， 造血和骨髓分化。这种相互作用促进靶mRNA降解， 维持一种无差别的状态。这些研究表明，ZFP 36 L2可以结合并降解 TIS 11/TTP家族的另外两个成员ZFP 36和ZFP 36 L1，创造了一个潜在的额外的 分化的转录后调节水平。抑制ZFP 36 L2恢复mRNA稳定性 并触发白血病细胞进行髓样分化， 凋亡一些原发性AML患者的表观基因组分析显示增强子模块 与不同AML细胞状态相关的ZFP 36 L2附近，建立了协调的表观遗传学 和形成白血病分化的转录后机制。在本申请中，我们最初 (Aim 1）关注ZFP 36 L2在AML中的体内作用，并鉴定mRNA，可以控制AML的直接靶点， AML细胞分化和生长。在目标2中，我们研究了ZFP 36/TIS 11家族的所有三个成员 并详细研究它们在造血和髓系白血病中的作用。

Abstract This application focuses on acute myeloid leukemia (AML), a blood cancer that is characterized by low survival rates and few available targeted therapies. The five-year overall survival rate for AML is below 30 percent in adults and around 65% in children. Interestingly, one type of intervention that has been successful for a subtype of AML (acute promyelocytic leukemia, APL) is a “differentiation” therapy, where drugs can induce tumor cell differentiation and apoptosis. Here we present surface antigen- guided, CRISPR/CAS9 differentiation screens in AML and study one of the most prominent hits in these screens, the RNA binding protein (RBP) ZFP36L2. RBPs can modify RNA at multiple levels, including splicing, processing, modification and degradation. Considering that RBPs are key regulators of gene expression, alterations of these proteins are also implicated in several human genetic diseases, including cancer. Our laboratory has recently presented CRISPR/CAS9 screening of RBPs in several types of human leukemia and identified novel regulators of the spliceosome machinery in blood cancers. Our CRISPR screens identified ZFP36L2, a member of the TIS11/TTP zinc-finger containing family of RBPs, that also includes the ZFP36 and ZFP36L1 paralogs. We were able to show that ZFP36L2 binds AU-rich elements on 3’ untranslated regions (UTRs) of a number of mRNAs that that control early hematopoietic and myeloid differentiation. This interaction promotes target mRNA degradation and the maintenance of an undifferentiated state. These studies showed that ZFP36L2 can bind and degrade the two other members of the TIS11/TTP family, ZFP36 and ZFP36L1, creating a potential additional level of post-transcriptional regulation of differentiation. Inhibition of ZFP36L2 restores mRNA stability of targeted transcripts and triggers leukemia cells to undergo myeloid differentiation and eventual apoptosis. Epigenomic profiling of a number of primary AML patients revealed enhancer modules nearby ZFP36L2 that associated with distinct AML cell states, establishing a coordinated epigenetic and post-transcriptional mechanism that shapes leukemic differentiation. In this application we initially (Aim 1) focus on the in vivo role of ZFP36L2 in AML and identify mRNAs, direct targets that can control AML cell differentiation and growth. In Aim 2, we study all three members of the ZFP36/TIS11 family and study in detail their roles in hematopoiesis and myeloid leukemia.