Nup98 Gene Rearrangements in Acute Myelogenous Leukemia

描述（由申请人提供）：核孔蛋白Nup98基因最近成为急性髓性白血病（AML）染色体重排的常见靶标。Nup98基因重排导致由Nup98的n端部分融合到至少15种不同蛋白质中的1种组成的嵌合蛋白的表达。在大多数情况下，融合伴侣是同源盒家族的转录因子。表征最好的Nup98嵌合体是Nup98-HOXA9，它包含Nup98的n端部分和同源盒转录因子HOXA9的dna结合域。Nup98-HOXA9在体外转化细胞并在小鼠模型中诱导AML。然而，其直接靶基因和引起白血病的机制尚不清楚。我们的初步数据表明，Nup98-HOXA9作为一种转录因子，比野生型HQXA9具有更强和更广泛的转录活性，而其他与白血病相关的转录因子，如AML1-ETO或PML-RARa，作为其野生型对应物的显性负抑制因子。此外，我们已经证明Nup98-HOXA9在体外扩展原始人类造血祖细胞。本课题的研究将验证Nup98-HOXA9是一种异常转录因子的假设，确定其作用机制，阐明其导致白血病的机制。我们将a)确定Nup98-HOXA9对原代人CD34+造血干细胞/祖细胞增殖、干细胞数量、分化、凋亡和细胞周期的影响，并鉴定介导这些影响的基因；b)证明Nup98-HOXA9是一种dna结合转录因子，并鉴定其直接靶基因和同源结合位点；c)鉴定nup98 - hoxa9相互作用蛋白及其对其功能的影响；d)阐明与野生型HOXA9相比，Nup98-HOXA9转录活性增加的基础；e)使用FISH分离探针鉴定具有Nup98基因重排的AML病例，鉴定这些病例中的异常基因表达模式，并将结果与体外转化的原代人CD34+造血干细胞/祖细胞的结果相关联。综上所述，这些研究将阐明Nup98-HOXA9促进白血病发生的机制，并确定可能作为潜在治疗靶点的关键靶基因、启动子结合位点和蛋白质相互作用。

DESCRIPTION (provided by applicant): The nucleoporin Nup98 gene has recently emerged as a frequent target of chromosomal rearrangements in acute myelogenous leukemia (AML). Nup98 gene rearrangements result in the expression of chimeric proteins consisting of the N-terminal portion of Nup98 fused to 1 of at least 15 different proteins. In most cases, the fusion partner is a transcription factor of the homeobox family. The best-characterized Nup98 chimera is Nup98-HOXA9, which contains the N-terminal portion of Nup98 and the DNA-binding domain of the homeobox transcription factor HOXA9. Nup98-HOXA9 transforms cells in vitro and induces AML in mouse models. However, its direct target genes and the mechanisms by which it causes leukemia are not known. Our preliminary data suggests that Nup98-HOXA9 acts as a transcription factor with a stronger and wider transcriptional activity than wild-type HQXA9, in contrast to other leukemia-associated transcription factors, such as AML1-ETO or PML-RARa, that act as dominant negative suppressors of their wild-type counterparts. In addition, we have shown that Nup98-HOXA9 expands primitive human hematopoietic progenitors in vitro. The studies in this proposal will test the hypothesis that Nup98-HOXA9 is an aberrant transcription factor, identify its mechanisms of action, and elucidate the mechanisms by which it causes leukemia. We will a) determine the effect of Nup98-HOXA9 on proliferation, stem cell numbers, differentiation, apoptosis, and cell cycle in primary human CD34+ hematopoietic stem/progenitor cells and identify the genes that mediate these effects; b) demonstrate that Nup98-HOXA9 is a DNA-binding transcription factor and identify its direct target genes and cognate binding sites; c) identify Nup98-HOXA9-interacting proteins and their effect on its functions; d) elucidate the basis for the increased transcriptional activity of Nup98-HOXA9 compared to wild-type HOXA9; and e) identify cases of AML with Nup98 gene rearrangements using a FISH break-apart probe, identify abnormal gene expression patterns in these cases, and correlate the findings with those obtained from in vitro-transformed primary human CD34+ hematopoietic stem/progenitor cells. Taken together, these studies will clarify the mechanisms by which Nup98-HOXA9 contributes to leukemogenesis and identify critical target genes, promoter binding sites, and protein interactions that could serve as potential targets for therapy.