Characterization of a Novel Translocation Product in APL

描述（由申请人提供）：急性早幼粒细胞白血病（APL）以早幼粒细胞水平的骨髓祖细胞成熟阻滞为特征。APL在白血病中是独特的，维甲酸诱导细胞分化，并诱导患者缓解。我们一直在探索APL的分子机制，以制定其他恶性肿瘤的分化治疗策略为长期目标。我们是第一个克隆APL的t(5; 17)（q35;q21）变体的研究小组。这种易位导致核磷蛋白（NPM）的n端117个氨基酸与维甲酸受体α (RARa)的c端403个氨基酸在框架内融合。NPM-RAR作为一种独特的“自然实验”，用于识别APL的共同分子机制。我们在细胞模型和转基因动物中发现，NPM- RAR表达可以阻断髓系分化。其他研究表明，截断的RARa仅含有RARa的c端403个氨基酸，不足以引起APL。事实上，我们的初步研究表明，NPM-RAR可能结合不与RARa相互作用的蛋白质。在本提案中，我们将确定NPM对NPM- rar蛋白功能的贡献。我们将验证NPM-RAR中的npm -序列对其产生APL表型的能力至关重要的假设。我们的具体目标是：1)确定npm -序列是否作为NPM-RAR的蛋白质相互作用域；2)确定NPM改变RARa转录活性的机制；3)确定NPM- rar是否抑制野生型NPM功能。这些研究将确定RARa融合伙伴在t(5; 17) APL中的作用，并将有助于确定APL表型背后的共同途径。急性髓性白血病（AML）是一个重大的公共卫生问题。了解NPM-RAR融合蛋白表达导致APL的详细机制可能有助于更深入地了解分化治疗的成功，并产生可应用于其他白血病的新治疗策略。此外，最近在大多数正常细胞遗传学AML患者中发现的NPM-重排增加了这些突变NPM研究的重要性，而不仅仅是在发现NPM- RAR的变型APL中。

DESCRIPTION (provided by applicant): Acute Promyelocytic Leukemia (APL) is characterized by a maturational arrest of bone marrow progenitors at the level of the promyelocyte. APL is unique amongst the leukemias in that retinoic acid induces differentiation of the blasts, and induces remissions in patients. We have been exploring the molecular mechanism underlying APL, with the long-term goal of developing strategies of differentiation therapy for other malignancies. We were the first group to clone the t(5; 17)( q35;q21) variant of APL. This translocation generates an in-frame fusion of the N-terminal 117 amino acids of nucleophosmin (NPM) with the C-terminal 403 amino acids of the retinoic acid receptor alpha (RARa). NPM-RAR serves as a unique "experiment of nature" with which to identify the common molecular mechanisms underlying APL. We have found that NPM- RAR expression can block myeloid differentiation, both in cell models and in transgenic animals. Others have shown that a truncated RARa that harbors just the C-terminal 403 amino acids of RARa is insufficient to cause APL. Indeed, our preliminary studies suggest that NPM-RAR may bind proteins that do not interact with RARa. In this proposal we will determine the contribution of NPM to the function of the NPM-RAR protein. We will test the hypothesis that the NPM-sequences within NPM-RAR are essential for its ability to generate the APL phenotype. Our Specific Aims are 1) to determine whether the NPM-sequences serves as a protein-interaction domain for NPM-RAR; 2) to determine the mechanism whereby NPM alters RARa transcriptional activity; 3) to determine whether NPM-RAR inhibits wild-type NPM function. These studies will identify the role of the RARa fusion partner in t(5; 17) APL, and will help identify common pathways that underlie the APL phenotype. Acute Myeloid Leukemia (AML) is a significant public health issue. Understanding the detailed mechanism whereby expression of the NPM-RAR fusion protein leads to APL may lead to deeper understanding of the success of differentiation therapy, and generate novel therapeutic strategies that can be applied to other leukemias. In addition, the recent finding of NPM-rearrangements in the majority of normal-cytogenetic AML patients increases the significance of these studies of mutated NPM beyond the variant APL in which NPM- RAR is found.