The functional role of snoRNAs in NPM1 wildtype and mutant AML

NPM 1突变是急性髓性白血病（AML）中最常见的突变之一。NPM 1是一种多功能的核仁伴侣蛋白，参与核糖体的生物合成和基因组的稳定性。NPM 1的突变在C-末端结构域产生新的核输出信号，并导致突变的NPM 1（NPM 1c）的异常胞质错位。基于其多效性功能，NPM 1基因改变在白血病发生中的作用已被提出几种机制。然而，NPM 1突变的AML的病理机制仍不完全清楚，小的非编码RNA（ncRNA）包括microRNA（miRNA）已被证明影响各种生理和细胞过程。我们以前确定C/D盒小核仁RNA（snoRNA）作为白血病干细胞活性的重要调节因子和AML 1-ETO诱导白血病发生的重要介质。为了评估C/D盒snoRNA在其他形式的AML中的潜在作用，我们在两个独立的患者队列中通过高通量小RNA-Seq分析了snoRNA表达。我们的初步数据显示，在两组中，C/D盒snoRNA在NPM 1野生型AML中高度表达，而在具有NPM 1突变的AML标本中表达低得多。值得注意的是，我们的质谱数据证明了野生型NPM 1和snoRNA表达调节因子DDX 21和AES之间的直接蛋白质-蛋白质相互作用。因此，我们的初步研究结果提供了证据，NPM 1在snoRNA表达的调节作用。为了进一步探索snoRNA在NPM 1野生型和突变型AML中的功能作用，我们提出：1）确定NPM 1对snoRNA调节的机制作用，并鉴定野生型和突变型NPM 1的蛋白质和RNA相互作用组; 2）在携带NPM 1突变与野生型的AML细胞中研究snoRNA失调对核糖体生物发生和功能的功能后果; 3）评估snoRNA下调在NPM 1c AML对化疗的有利反应中的潜在作用以及snoRNA抑制在AML对化疗敏感性中的效用。这些数据将提高我们对NPM 1突变AML病理学的理解，并进一步揭示C/D盒snoRNA通路在异常造血中的重要作用。

NPM1 mutations rank among the most frequent mutations in acute myeloid leukemia (AML). NPM1 is a multifunctional nucleolar chaperone involved in ribosome biogenesis and genomic stability. Mutations in NPM1 generate a novel nuclear export signal in the C-terminal domain and lead to aberrant cytoplasmic dislocation of mutated NPM1 (NPM1c). Based on its pleiotropic functions, several mechanisms have been proposed for the contribution of NPM1 gene alterations to leukemogenesis. However, the pathology of NPM1-mutated AML remains incompletely understood.Small non-coding RNAs (ncRNAs) including microRNA (miRNA) have been shown to impact onto various physiological and cellular processes. We previously identified C/D box small nucleolar RNAs (snoRNA) as crucial regulators of leukemia stem cell activity and essential mediator of AML1-ETO induced leukemogenesis. To evaluate a potential role of C/D box snoRNAs in other forms of AML, we profiled snoRNA expression by high throughput small RNA-Seq in two independent cohorts of patients. Our preliminary data shows that in both sets C/D box snoRNAs are highly expressed in NPM1 wildtype AML whereas expression are much lower in AML specimens with NPM1 mutations. Of note, our mass spectrometry data demonstrates a direct protein-protein interaction between wildtype NPM1 and the snoRNA expression regulators DDX21 and AES. Thus, our preliminary findings provide evidence for a regulatory role of NPM1 in snoRNA expression. To further explore the functional role of snoRNAs in NPM1 wildtype and mutant AML, we propose to 1) define the mechanistic role of NPM1 for snoRNA regulation and to identify the protein and RNA interactome of wildtype and mutant NPM1; 2) investigate the functional consequences of snoRNA deregulation on ribosome biogenesis and function in AML cells harboring NPM1 mutation versus wildtype; 3) evaluate the potential role of snoRNA downregulation in the favorable response of NPM1c AML to chemotherapy and the utility of snoRNA suppression in sensitizing AML to chemotherapy. Together these data will improve our understanding of pathology of NPM1-mutated AML, and further uncover the essential role of C/D box snoRNA pathway in aberrant hematopoiesis.