A B-CELL SPECIFIC COFACTOR OF NUCLEOSOME REMODELING

免疫球蛋白分子（Ig）由重链和轻链组成，在b细胞中表达多种抗原。igg在DNA缺失过程中获得抗原识别特性，称为VDJ重组。重组Ig的不成功表达会导致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Ig表达的调控部分受靶向Ig位点的转录和VDJ重组酶活性的调控。最近的实验表明，Ig位点的选择性染色质重组可能以B细胞特异性的方式控制转录和重组酶活性的可及性。本研究提出的实验利用Abelson细胞系中诱导轻链（kappa）基因重组来开发高度纯化的体外系统，该系统忠实地模拟了VDJ重组信号的Ig位点重塑。该系统将研究Abelson细胞中存在的一种内源性活性，该活性要么特异性识别并直接重塑，要么特异性识别并招募kappa位点的“一般重塑机制”，以在诱导VDJ重排时进行染色质重组。

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.