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蛋白的易位，如HOXA9，与急性胰腺炎的发病机制有关。 髓系白血病(AML)。我们对HOX蛋白细胞内水平和活性的理解 在造血过程中被控制，目前仅限于转录调节和信号转导。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是如何- 依赖蛋白的降解调节正常和恶性的造血。的核心假说 应用是cullin 4A(CuL-4A)泛素连接酶通过靶向调控造血发育 关键的造血调节剂的降解。这一假设是在强有力的初步假设的基础上提出的 数据表明，CuL-4A靶向HOXA9进行降解，并调节髓系分化和 成熟。小鼠血液学特异性敲除CuL-4A基因导致骨量增加 骨髓祖细胞和外周血白细胞。这项建议旨在确定生物化学 HOXA9依赖于CuL-4A的蛋白降解控制和染色体易位的机制- 衍生的NUP98-HOXA9融合，并阐明CuL-4A在抑制白血病中的功能意义 转型。我们特别准备进行这项拟议的研究，因为我们最近才产生了 抗CuL-4A的HOXA9突变体，并发展了条件CUL-4A基因敲除小鼠和CuL-4A siRNA以消除或 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传递系统，以实现高效 原代造血干和祖细胞的转导。我们建议将生化和生物化学相结合 周鹏波博士实验室的分子遗传学方法和体内外造血分析技术 在马尔科姆·摩尔博士的实验室中，以解决以下具体目标：(1)定义 依赖CuL~4A的HOXA9泛素化和降解(2)阐明HOXA9的功能意义 急性髓系白血病发病机制中CuL-4A的降解作用。(3)确定CuL-4A抗性的分子基础 白血病NUP98-HOXA9融合及CuL-4A消融对NUP98-HOXA9小鼠模型的影响 HOXA9诱导的白血病。由于几乎没有关于蛋白质降解的作用的信息。 白血病的发生，这一提议的成功完成将代表着在理解一部小说方面的重大进步 翻译后机制，管理关键的造血调节因子的功能，并提供一个框架 未来在正常和恶性造血中靶向蛋白质降解的研究。

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.