A B-CELL SPECIFIC COFACTOR OF NUCLEOSOME REMODELING

免疫球蛋白分子（IG）由重链和轻链组成，并在B细胞中表达以产生多种抗原。Ig在称为VDJ重组的DNA缺失过程中获得其抗原识别特性。重组IG的不成功表达导致B细胞成熟失败、大量感染和受影响个体的过早死亡。Abelson细胞系具有前B细胞的表型，并已用于研究IG表达如何影响B细胞成熟。可及性假说提出，B细胞中受调节的IG表达部分由靶向IG基因座的转录和VDJ重组酶活性控制。最近的实验表明，选择性染色质重组的IG基因座可能发挥作用，在控制可及性转录和重组酶活动的B细胞特异性的方式。本研究中提出的实验利用Abelson细胞系中的诱导型轻链（κ）基因重组来开发高度纯化的体外系统，该系统忠实地模拟VDJ重组信号IG基因座重塑。该系统将研究Abelson细胞中内源性存在的拟议活性，该活性特异性识别并直接重塑或特异性识别并招募“一般重塑机制”至κ基因座，以在诱导VDJ重排后进行染色质重组。

Immunoglobulin molecules (Ig) consist of heavy and light chains and are expressed in B-cells to diversity of antigens. Igs acquire their antigen recognition properties in a process of DNA deletion called VDJ recombination. Unsuccessful expression of the recombined Ig leads to failure of B-cell maturation, numerous infections and premature death of the affected individual. Abelson cell lines have the phenotype of a pre-B- cell and have been used to study how Ig expression affects B-cell maturation. The accessibility hypothesis proposes that regulated Ig expression in B-cells is governed in part by the transcriptional and VDJ recombinase activities to target the Ig locus. Recent experiments suggest that selective chromatin reorganization of the Ig locus may play a role in controlling accessibility to transcriptional and recombinase activities in B- cell-specific manner. The experiments proposed in this fellowship exploit inducible light chain (kappa) gene reorganization in Abelson cell lines to develop a highly purified in vitro system that faithfully mimics VDJ recombination signaled Ig locus remodeling. This system will investigate a proposed activity endogenously present in Abelson cells that either specifically recognizes and directly remodels or specifically recognizes and recruits a "general remodeling machinery" to the kappa locus for chromatin reorganization upon induction of VDJ rearrangement.