Function and Regulation of Early B Cell Factor (EBF)

描述(申请人提供)：早期B细胞因子(EBF)是B淋巴细胞基因的重要调节因子。EBF通过激活编码前B细胞和成熟B细胞受体(前BCR和BCR)的基因，推动B细胞从早期祖细胞发育到成熟B细胞。在缺乏EBF的小鼠中，B细胞发育受阻，不产生免疫球蛋白，EBF靶基因也不被激活。在缺乏EBF的情况下，mb-1(Ig-a)基因仍然存在于高甲基化的、难以获得的染色质中。最近，我们证明了EBF是B细胞特异性mb-1启动子上的CpG去甲基化和核小体重塑所必需的。EBF对染色质的重塑有助于B谱系承诺因子Pax5与启动子的结合。我们的研究发现了一个新的“功能”转录因子层次结构，它除了先前确定的“遗传”层次结构(EBF调节Pax5的表达)之外还起作用。我们提出，EBF确定B系在很大程度上是由于其作为染色质重塑“先锋因子”的重要作用。为了了解EBF如何驱动B系决定，我们建议1)确定EBF在B系指定中重要的基因靶点，2)确定EBF如何启动mb-1启动子的去甲基化，3)确定EBF依赖的染色质重塑的分子基础。

DESCRIPTION (provided by applicant): Early B cell Factor (EBF) is an essential regulator of genes in B lymphocytes. EBF drives B cell development from early progenitors to mature B cells by activating genes encoding the pre-B and mature B cell receptors (pre-BCR and BCR). In mice lacking EBF, B cell development is arrested, immunoglobulins are not produced and EBF target genes are not activated. In the absence of EBF mb-1 (Ig-a) genes remain in hypermethylated, inaccessible chromatin. Recently, we demonstrated that EBF is required for, and indeed, initiates CpG demethylation and remodeling of nucleosomes at the B cell-specific mb-1 promoter. Remodeling of chromatin by EBF facilitates binding of the promoter by the B lineage commitment factor Pax5. Our studies identified a new 'functional' hierarchy of transcription factors that acts in addition to the 'genetic' hierarchy identified previously (EBF regulates expression of pax5). We have proposed that B lineage determination by EBF is largely a function of its essential role as a chromatin remodeling 'pioneer factor'. To understand how EBF drives B lineage determination, we propose to 1) identify gene targets of EBF that are important in B lineage specification, 2) determine how EBF initiates demethylation of the mb-1 promoter and 3) determine the molecular basis of EBF-dependent chromatin remodeling.