AETFC转录因子复合物的翻译后修饰在急性髓系白血病中的作用机制的研究

The AML1-ETO-containing transcription factor complex (AETFC) is a novel multiprotein complex that was recently identified from acute myeloid leukemia (AML) cells by our group. This complex contains the leukemogenic fusion protein AML1-ETO and several important hematopoietic transcription factors. We previously have demonstrated that AETFC is required for leukemia stem cell self-renewal and leukemogenesis. The following key question to be answered is how AETFC is regulated in terms of its structure and function, i.e., how AETFC interacts with the variety signaling transduction pathways in the leukemia cells. Protein post-translational modification (PTM) is an important mechanism for cellular signaling transduction; many transcription factors are modified and thereby functionally regulated by different signals in the cell. This project is based on the newly discovered PTMs in AETFC, including the acetylation and methylation of AML1-ETO and an ubiquitin-like modification of HEB, which likely regulate the activity and stability of AETFC. We will combine biochemistry, epigenomics, cell biology and mouse leukemia modeling technical systems to systematically analyze the PTMs on AETFC, and to study the detailed mechanism by which how these PTMs are generated and how they regulate the biological functions of AETFC in leukemogenesis. Moreover, we will evaluate whether the enzymes that catalyze the PTMs, as well as the PTM-mediated protein-protein interactions, could be druggable for therapeutics. These studies should not only contribute to better understanding of the mechanisms of leukemogenesis, but also provide new therapeutic strategies for leukemia treatment.

AETFC是我们最近从急性髓系白血病细胞中发现的一个新的多蛋白复合物，它包含致病融合蛋白AML1-ETO以及多个关键的造血系统特异的转录因子。我们已经证明AETFC对于白血病干细胞自我更新和白血病发病是必需的，而接下来亟待回答的关键问题是：AETFC的结构和功能如何被调控，即如何与细胞的各种信号转导调控机制建立联系？蛋白的转录后修饰是细胞信号转导的一种重要方式，许多转录因子都是通过被修饰从而调控其功能。本课题将从我们最近发现的AETFC的乙酰化、甲基化和类泛素化入手，结合生物化学、细胞生物学和白血病小鼠模型，系统分析AETFC的翻译后修饰，深入研究这些修饰如何发生以及如何影响AETFC在白血病细胞中的功能。同时，我们也将研究控制这些修饰的酶以及这些修饰所介导的相互作用是否适合作为药物作用靶点。对这些问题的探索不仅能够使我们更加深入地理解白血病的发病机制，也可望为白血病的治疗提供新的策略。

AETFC是我们从t(8;21)急性髓系白血病细胞中发现的一个新的多蛋白复合物，它包含致病融合蛋白AML1-ETO以及多个关键的造血系统特异的转录因子，能够维持t(8;21)白血病细胞的转录调控网络，对白血病的发病至关重要。本项目试图回答的关键问题是：AETFC的结构和功能如何被调控？我们从AETFC成员蛋白的翻译后修饰和差异表达入手，结合生物化学、细胞生物学、白血病小鼠模型以及病人随访等方法，着重研究了AETFC的异质性和稳定性两个方面的调控机制。代表性研究成果包括：（1）我们发现AETFC的三个重要成员蛋白E2-2、E2A和HEB（统称为E蛋白）能够界定AETFC的异质性，其中E2-2能够作为一个白血病的负向调控因子，使得AETFC特异性识别并激活树突状细胞（DC）分化相关基因，从而促使白血病细胞向DC分化，进而调控白血病细胞的异质性，而且这种异质性与t(8;21)白血病病人的预后相关，并由此使我们得以鉴定可预测白血病复发的潜在生物标志物。（2）我们发现AETFC的稳定性可由其核心成员蛋白LYL1所控制，髓系转录因子C/EBPalpha能够通过直接抑制LYL1基因的转录引起AETFC的解聚进而降解，这一调控机制在白血病细胞分化过程中起到重要作用。除此以外，我们还研究了负责AML1-ETO乙酰化的乙酰基转移酶TAF1对于白血病发病的调控作用等方面。综上所述，这些研究结果揭示了t(8;21)白血病发病过程中的精确调控机制，建立了这些调控机制与白血病预后之间的关联，发现了可用于预测白血病复发的潜在的肿瘤标志物，并提示了新的靶向治疗策略。