Regulation of B Cell Development and Function by Zfp521

描述（由申请人提供）：骨髓中B细胞发育的概述是从多能造血干细胞（HSC）到定向未成熟B淋巴细胞的逐步过程。研究已经阐明了早期B细胞发育所必需的转录因子的B细胞特异性调节网络。这些蛋白质包括早期B细胞因子1（EBF 1），其驱动B谱系特化和定型。虽然对EBF 1了解很多，但关于其在B细胞中的调节及其蛋白质-蛋白质相互作用的潜力，仍有许多未解答的问题。有几条证据表明Zfp 521（Evi 3/ZNF 521/EHZF）是与EBF 1共同调控基因转录的因子。Zfp 521与EBF 1发生物理相互作用，并在体外抑制其活性。Zfp 521在发育中的B细胞中与EBF 1共表达。然而，关于Zfp 521在B细胞发育中的功能知之甚少。具体而言，Zfp 521调节EBF 1活性的机制以及Zfp 521和EBF 1之间物理相互作用的基础和后果尚不清楚。 我们已经证明，早期B细胞发育在Zfp 521不存在的情况下受到极大的干扰。这通过Zfp 521缺陷小鼠骨髓中晚期前B细胞和前B细胞的标志物表达的缺乏以及未成熟B细胞的减少来证明。作为一种整合Zfp 521和EBF 1活性的机制，我们实验室最近的研究使用新开发的抗体试剂检测到Zfp 521与也结合EBF 1的启动子结合。Zfp 521和EBF 1在这些基因上的共占据提示了B淋巴细胞生成的共调节的新模型。以这种方式，在发育中的B细胞中，B谱系决定因子EBF 1受Zfp 521调节。假设：Zfp 521对B细胞淋巴细胞生成和功能至关重要。我们认为它通过EBF 1依赖性和非依赖性机制调节B细胞程序。Zfp 521与EBF 1相互作用以限制其DNA结合，但Zfp 521也与靶基因DNA上的EBF 1组装复合物。在分子水平上确定EBF 1和Zfp 521之间相互作用的基础对于理解B细胞调控网络如何产生能够在体液免疫应答中分泌抗体的成熟B细胞至关重要。因此，我们将：确定Zfp 521如何调节发育中的B细胞的基因转录。通过鉴定前B细胞中Zfp 521的结合位点，确定Zfp 521在B细胞调控网络中的功能。定义Zfp 521与EBF 1相互作用的结构要求和功能后果。

DESCRIPTION (provided by applicant): Summary B cell development in the bone marrow proceeds in a stepwise process from multipotent hematopoietic stem cells (HSCs) to committed immature B lymphocytes. Research has elucidated a B cell-specific regulatory network of transcription factors necessary for the development of early B cells. These proteins include Early B cell Factor 1 (EBF1), which drives B lineage specification and commitment. Although much is known about EBF1, there are many unanswered questions concerning its regulation in B cells and its potential for protein- protein interactions. Several lines of evidence point to Zfp521 (Evi3/ZNF521/EHZF) as a co-regulator of gene transcription with EBF1. Zfp521 interacts physically with EBF1 and can repress its activity in vitro. Zfp521 is co- expressed with EBF1 in developing B cells. However, little is known concerning functions of Zfp521 in B cell development. Specifically, the mechanisms by which Zfp521 modulates activities of EBF1 and the basis and consequences of physical interactions between Zfp521 and EBF1 are unknown. We have demonstrated that early B cell development is perturbed greatly in the absence of Zfp521. This is evidenced by a lack of expression of markers of late pro-B cells and pre-B cells and decreased immature B cells in bone marrow of Zfp521-deficient mice. As a mechanism that integrates the activities of both Zfp521 and EBF1, recent studies in our laboratory using newly developed antibody reagents detected Zfp521 binding to promoters that also bind EBF1. Co-occupancy of Zfp521 and EBF1 on these genes suggests a new model for co-regulation of B lymphopoiesis. In this manner, EBF1, the B lineage determination factor, is regulated by Zfp521 in developing B cells. Hypotheses: Zfp521 is critically important for B cell lymphopoiesis and function. We propose that it regulates the B cell program via EBF1-dependent and -independent mechanisms. Zfp521 interacts with EBF1 to limit its DNA binding, but Zfp521 also assembles complexes with EBF1 on target gene DNA. Determining the basis of interactions between EBF1 and Zfp521 at the molecular level is critical for understanding how the B cell regulatory network generates mature B cells capable of secreting antibodies in humoral immune responses. Therefore, we will: Determine how Zfp521 regulates gene transcription in developing B cells. Determine how Zfp521 functions in the B cell regulatory network by identifying its binding sites in pro- B cells. Define structural requirements and functional consequences of Zfp521 interactions with EBF1.