Ubiquitin-Proteolytic Control of HOXA9 in Leukemogenesis

HOXA9 在白血病发生中的泛素蛋白水解控制

• 批准号: 7016787
• 负责人: Pengbo Zhou
• 金额: $ 31.62万
• 依托单位: WEILL MEDICAL COLL OF CORNELL UNIV
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-01-27 至 2010-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7016787
• 关键词: acute myelogenous leukemia; bone marrow; carcinogenesis; hematopoiesis; leukemia; model; mutant; protein degradation; proteins; ubiquitin

DESCRIPTION (provided by applicant): 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 is known 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 degradation regulates normal and malignant hematopoiesis. The central hypothesis of the application is that the cullin 4A (CUL-4A) ubiquitin-ligase controls hematopoietic development through targeted degradation of key hematopoietic regulators. The hypothesis has been formulated on the basis of strong preliminary data, which demonstrated that CUL-4A targets HOXA9 for degradation, and regulates myeloid differentiation and 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 generated a 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 systems for efficient transduction in primary hematopoietic stem and progenitor cells. We propose to combine the biochemical and molecular genetic approaches in Dr. Pengbo Zhou's lab and the expertise in ex vivo and in vivo hematopoietic analysis 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 resistance by the leukemogenic NUP98-HOXA9 fusion 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 framework for future investigations of targeted protein degradation in normal and malignant hematopoiesis.

描述(申请人提供)：HOX同源结构域(HD)蛋白是造血的关键调节因子。涉及某些HOX蛋白的异常表达或染色体易位，如HOXA9，与急性髓系白血病(AML)的发病机制有关。我们目前对造血过程中HOX蛋白的细胞内水平和活性的控制仅限于转录调控和信号转导。关于HOX造血调节因子丰度的翻译后调控机制以及此类调控的功能意义，我们知之甚少。这项研究的长期目标是了解泛素依赖的蛋白质降解是如何调节正常和恶性造血的。该应用的中心假设是，cullin 4A(CuL-4A)泛素连接酶通过定向降解关键的造血调节因子来控制造血发育。这一假说是建立在强大的初步数据基础上的，这些数据表明，CUL-4A针对HOXA9进行降解，并调节髓系的分化和成熟。在小鼠中，造血特异性敲除CuL-4A基因导致骨髓祖细胞和外周血白细胞增加。本研究试图确定HOXA9依赖于CuL-4A的蛋白降解调控和染色体易位导致的NUP98-HOXA9融合的生化机制，并阐明CuL-4A在抑制白血病转化中的功能意义。我们为开展这项拟议的研究做好了独特的准备，因为我们最近产生了一个抗CuL-4A的HOXA9突变体，并开发了条件CUL-4A基因敲除小鼠和CuL-4A siRNA来消除或调节CuL-4A的活性。我们还优化了慢病毒和逆转录病毒为基础的基因传递系统，以便在初级造血干细胞和祖细胞中进行有效的转导。我们建议将周鹏波博士实验室的生化和分子遗传学方法与马尔科姆·摩尔博士的实验室在体外和体内造血分析方面的专业知识结合起来，以解决以下具体目标：(1)确定依赖CuL-4A的泛素化和HOXA9降解的生化机制。(2)阐明CuL-4A降解HOXA9在AML发病机制中的功能意义。(3)探讨白血病细胞株NUP98-HOXA9融合后产生CuL-4A耐药的分子基础，以及在NUP98-HOXA9诱导的小鼠白血病模型中去除CuL-4A的影响。由于目前关于蛋白质降解在白血病发生中的作用的信息很少，这一提议的成功完成将代表着在理解调控关键造血调节因子功能的新的翻译后机制方面取得了重大进展，并为未来研究正常和恶性造血中的靶向蛋白质降解提供了一个框架。