Ufm1类泛素化修饰系统调节红细胞生成的分子机制

Erythropoiesis plays an important role in human health, and dysfunction of this fundamental process leads to leads to disease pathogenesis ranging from anemia to leukemia. Ufm1 (ubiquitin-fold modifier 1) conjugation system is a novel ubiquitin-like (Ubl) system that shares biochemical features with other ubiquitin systems, but its target(s) and biological functions remain poorly defined. Genetic study from Uba5 (E1 enzyme for Ufm1 conjugation or ufmylation) knockout mice has shown that Uba5 is indispensable for embryonic erythropoiesis, underscoring the essential role of this novel Ubl system in erythropoiesis, yet the underlying mechanism remains completely unclear. RCAD protein is a novel Ufm1 E3 ligase that promotes ufmylation of ASC1, a co-activator of nuclear receptor signaling. Ufmylation of ASC1 is crucial for recruitment of other transcription factors and promotion of nuclear receptor-mediated transcription. As one of the first groups who have identified RCAD independently, we have succeeded to create RCAD knockout (KO) and conditional knockout (CKO) mice. Our preliminary study has demonstrated that RCAD is essential for both embryonic and adult erythropoiesis. In this proposed project, we will take advantage of in vitro culture and differentiation of primary fetal liver erythroid progenitor cells to gene expression profiling techniques to investigate the role of ufmylation in erythropoiesis. The outcome of this project will provide a new anemic animal model and a novel mechanism to regulate erythropoiesis. This study will facilitate our understanding of the biological function and working mechanism of the Ufm1 conjugation system, provide new candidate genes and mechanistic insight for certain congenital and acquired anemias, and ultimately establish a novel therapeutic target for treatment of anemic diseases.

红细胞生成功能的失调会造成包括贫血和癌症等血液学疾病。Ufm1类泛素化修饰系统是一新的类泛素化系统，其生物学功能最近才被认知。Ufm1 E1酶Uba5敲除小鼠的研究表明它在胚胎红细胞生成中起到关键作用,但在成年红细胞生成的作用仍有待阐明。RCAD 蛋白是一个Ufm1E3连接酶，能促进核受体转录辅助因子ASC1的Ufm1类泛素化。而ASC1的Ufm1类泛素化为招募其它转录因子提供了一个结合平台。作为鉴定RCAD的实验室之一，我们成功建立了RCAD基因敲除小鼠。前期工作显示RCAD在红细胞生成过程中起着不可缺失的作用。在本课题中，我们将利用原代胚肝红细胞体外培养和分化以及基因表达谱分析技术研究Ufm1类泛素化在红细胞生成中的作用和机理。本课题预期结果将提供一全新贫血动物模型和红细胞生成调控机制,为探索先天性红细胞生成异常及后天性贫血提供新的候选基因和理论依据,最终为治疗贫血性疾病开辟新途径。

本项目进行了以下研究工作：Ufm1类泛素化修饰系统在胚胎肝细胞发生中作用；Ufm1底物ASC1在胚胎肝细胞发生中作用；Ufm1类泛素化修饰对红细胞前体细胞的基因调控；体内验证ASC1泛素化修饰在骨髓红细胞造血过程中对转录因子的调控；Ufm1类泛素化修饰对内质网应激反应的调控; 以及小分子化合物Salubrinal对Ufmylation相关基因的调控和贫血表型的影响。该项目完成了预期研究目标。本课题提供一个全新的贫血动物模型和红细胞生成调控机制。同时，对Ufm1 类泛素化修饰系统的生物学功能及机理的研究起到极大的促进作用。为进一步探索先天性红细胞生成异常性贫血及后天性贫血提供新的候选基因和理论依据，最终为治疗贫血性疾病开辟新途径。