Ubiquitin-Proteolytic Control of HOXA9 in Leukemogenesis

HOX同源结构域（HD）蛋白是造血的关键调节因子。异常表达或染色体 涉及某些HOX蛋白（如HOXA 9）的易位与急性胰腺炎的发病机制有关。 骨髓性白血病（AML）。我们对HOX蛋白的细胞内水平和活性的理解是如何影响 造血过程中的控制目前仅限于转录调控和信号转导。鲜为人知 关于控制HOX造血调节因子丰度的翻译后控制机制， 这类法规的功能意义。这项研究的长期目标是了解泛素- 依赖性蛋白质降解调节正常和恶性造血。的中心假设 cullin 4A（CUL-4A）泛素连接酶通过靶向调控造血发育， 关键造血调节因子的降解。这一假设是在强有力的初步证据的基础上提出的。 数据表明，CUL-4A靶向HOXA 9降解，并调节骨髓分化， 成熟造血特异性敲除小鼠CUL-4A基因导致骨扩张增加 骨髓祖细胞和外周血白细胞。该提案旨在确定生物化学 CUL-4A依赖的HOXA 9蛋白水解控制和染色体易位的潜在机制- 目的：探讨CUL-4A在抑制白血病细胞增殖中的作用。 转型我们已做好独特的准备进行拟议的研究，因为我们最近产生了a CUL-4A抗性HOXA 9突变体，并开发了条件性CUL-4A敲除小鼠和CUL-4A siRNA以消除或抑制CUL-4A抗性HOXA 9突变体。 调节CUL-4A活性。我们还优化了基于慢病毒和逆转录病毒的基因递送系统， 在原代造血干细胞和祖细胞中的转导。我们建议联合收割机生物化学和 Pengbo Zhou博士实验室的分子遗传学方法以及体外和体内造血分析的专业知识 在马尔科姆摩尔博士的实验室，以解决以下具体目标：（1）定义的生化机制， CUL~ 4A依赖的泛素化和HOXA 9的降解。(2)阐明HOXA 9的功能意义 CUL-4A在AML发病机制中的降解。(3)确定CUL-4A抗性的分子基础， 在致白血病NUP 98-H 0XA 9融合的小鼠模型中评估CUL-4A消融的影响。 HOXA 9诱导的白血病。由于很少有关于蛋白质降解过程中的作用的信息， 白血病，成功完成这项建议将代表一个重大进展，了解一个新的 翻译后机制，控制关键造血调节因子的功能，并提供一个框架， 在正常和恶性造血中靶向蛋白降解的未来研究。

The HOX homeodomain (HD) proteins are key regulators of hematopoiesis. Aberrant expression or chromosomal translocations involving certain HOX proteins, such as HOXA9, have been implicated in the pathogenesis of acute myeloid leukemia (AML). Our understanding of how the intracellular levels and activities of the HOX proteins are controlled during hematopoiesis is current limited to transcriptional regulation and signal transduction. Little isknown about the posttranslational control mechanisms that govern the abundance of the HOX hematopoietic regulators and the functional significance for such regulations. The long-term goal of this study is to understand how ubiquitin- dependent protein degradationregulates normal and malignant hematopoiesis. The central hypothesis of the application is that the cullin 4A (CUL-4A) ubiquitin-ligase controls hematopoietic development throughtargeted degradation of key hematopoietic regulators. The hypothesis has been formulated on the basis of strong preliminary data, which demonstratedthat CUL-4A targets HOXA9 for degradation, and regulates myeloid differentiationand maturation. Hematopoietic-specific knockout of the CUL-4A gene in mice led to an increased expansion of bone marrow progenitor cells and peripheral blood leukocytes. This proposal seeks to determine the biochemical mechanisms underlying the CUL-4A-dependent proteolytic control of HOXA9 and the chromosomal translocation- derived NUP98-HOXA9 fusion, and to elucidate the functional significance of CUL-4A in suppressing leukemic transformation. We are uniquely prepared to undertake the proposed research, since we have recently generateda CUL-4A-resistant HOXA9 mutant, and developed conditional CUL-4A knockout mice and CUL-4A siRNA to eliminate or modulate CUL-4A activity. We have also optimized lentiviral- and retroviral-based gene delivery systemsfor efficient transduction in primary hematopoietic stem and progenitor cells. We propose to combine the biochemical and molecular genetic approachesin Dr. Pengbo Zhou's lab and the expertise in ex vivo and in vivo hematopoieticanalysis in Dr. Malcolm Moore's lab to address the following specific aims: (1) to define the biochemical mechanisms underlying CUL~4A-dependent ubiquitination and degradation of HOXA9. (2) to elucidate the functional significance of HOXA9 degradation by CUL-4A in the pathogenesis of AML. (3) to determine the molecular basis for CUL-4A resistanceby the leukemogenic NUP98-HOXA9fusion and to assess the impact of CUL-4A ablation in the mouse model of NUP98- HOXA9-induced leukemia. Since little information is available regarding the roles of protein degradation during leukemogenesis, successful completion of this proposal will represent a significant advance in understanding a novel posttranslational mechanism that governs the functions of key hematopoietic regulators, and provide a frameworkfor future investigations of targeted protein degradation in normal and malignant hematopoiesis.