DCAF1(VprBP) regulates FoxO1 to promote Rag transcription

项目总结 B和T淋巴细胞构成了我们适应性免疫系统的基础，它基于特定的 通过结构不同的表面抗原受体识别外源分子。这些地区的结构多样性 受体起源于淋巴细胞中抗原受体基因的特异性重排 发展。这种重排过程被称为V(D)J重组，当RAG1/2蛋白启动时 在抗原受体基因片段引入DNA双链断裂(DSB)，并在 双链断裂是通过非同源末端连接来感知和修复的。这一过程经历了许多层次的 但限制V(D)J重组的一个基本手段是控制RAG的水平 蛋白质本身。该实验室的工作表明，RAG1水平受RAG1相互作用的控制 我们确定的一种蛋白质称为VPR结合蛋白(VprBP；也称为DCAF1)，它通过 两种不同的机制：第一，通过促进蛋白酶体依赖的RAG1的及时降解 VprBP与CUL4-DDB1 E3泛素连接酶复合体的结合；第二，通过调节RAG 在刺激V(D)J重组的条件下进行转录诱导。潜在的详细信息 第二个机制仍不清楚。然而，最近的研究发现VprBP具有潜在的调节作用 与RAG表达所需的关键转录因子FoxO1直接相互作用，其方式是 对FoxO1乙酰化状态敏感。这些发现使我们假设VprBP(DCAF1)在 乙酰化依赖与FoxO1的结合来调节RAG转录诱导。为了测试这一点 假设，我们将(I)确定VprBP是否介导乙酰化依赖的与FoxO1和FoxO1的关联 影响其定位；以及(Ii)测试FoxO1乙酰化是否调节FoxO1沉积到RAG位点， RAG转录激活和V(D)J重组，以VprBP依赖的方式进行。建立 VprBP-FoxO1相互作用的分子基础，它们对乙酰化的依赖，以及乙酰化对 RAG的表达将定义VprBP在V(D)J重组中的新的生理作用，并暴露出潜在的 RAG表达异常引起的免疫系统改变和基因组不稳定的来源。这 这项工作还将为理解VprBP如何调控FoxO1依赖的转录提供一个范例。 激活其目标基因，这将进一步扩大该项目的科学兴趣，并有可能 揭示从治疗角度调节FoxO1依赖基因表达的新途径。

PROJECT SUMMARY B and T lymphocytes form the foundation of our adaptive immune system, which is based on specific recognition of foreign molecules by structurally diverse surface antigen receptors. Structural diversity in these receptors originates through site-specific rearrangement of the antigen receptor genes during lymphocyte development. This rearrangement process, called V(D)J recombination, is initiated when the RAG1/2 proteins introduce DNA double-strand breaks (DSBs) at antigen receptor gene segments, and is completed when the DSBs are sensed and repaired by non-homologous end-joining. This process is subjected to many layers of regulation, but an elementary means to constrain V(D)J recombination is to control the level of the RAG proteins themselves. Work in this laboratory suggests that RAG1 levels are controlled by a RAG1 interacting protein we identified called Vpr binding protein (VprBP; also called DCAF1), which exerts its control through two different mechanisms: first, by promoting timely proteasome-dependent degradation of RAG1 through VprBP’s association with a Cul4-DDB1 E3 ubiquitin ligase complex; and second, by regulating Rag transcriptional induction under conditions that stimulate V(D)J recombination. The details underlying the second mechanism remain unclear. However, recent studies have identified VprBP as potentially mediating direct interactions with a key transcription factor required for Rag expression, called FoxO1, in a manner that is sensitive to FoxO1 acetylation status. These findings lead us to hypothesize that VprBP(DCAF1) mediates acetylation-dependent association with FoxO1 to regulate Rag transcriptional induction. To test this hypothesis, we will (i) establish whether VprBP mediates acetylation-dependent association with FoxO1 and influences its localization; and (ii) test whether FoxO1 acetylation regulates FoxO1 deposition to the Rag locus, Rag transcriptional activation, and V(D)J recombination, in a VprBP-dependent manner. Establishing the molecular basis for VprBP-FoxO1 interactions, their reliance on acetylation, and the influence of acetylation on Rag expression would define a new physiological role for VprBP in V(D)J recombination, and exposes potential sources for altered immune repertoire and genomic instability caused by dysregulated Rag expression. This work would also provide a paradigm for understanding how VprBP regulates FoxO1-dependent transcriptional activation of its target genes, which would further broaden the scientific interest of the project and potentially reveal new avenues to therapeutically regulate FoxO1-dependent gene expression.