Transcriptional Control of AICDA Expression

描述（由申请人提供）：免疫球蛋白体细胞超突变和类转换重组增加特异性和扩展抗体库的功能，以响应抗原挑战，提供更好的抗感染保护。这两个过程都涉及成熟B淋巴细胞基因组的高度有序、时间不稳定。这种基因组不稳定的调控在控制淋巴肿瘤发生中似乎是至关重要的。一个重要的调控机制是激活诱导胞苷脱氨酶（AICDA）基因表达的转录控制。AICDA为高突变和类开关重组提供了中心催化活性，是这两个过程中唯一已知的淋巴细胞特异性成分，其转录主要局限于生发中心b淋巴细胞。表征AICDA基因表达的转录控制对于理解高突变和类开关重组的生理调控至关重要，并且可以阐明导致不受控制的基因组不稳定和肿瘤发生的潜在病理畸变。我们对AICDA基因在小鼠b细胞系中的转录进行了表征，确定了在已建立的细胞系和原代脾b细胞中的转录起始位点，并鉴定了一个进化保守的AICDA基因的推定启动子。在本申请中，我们建议进行实验：i)确定AICDA基因座内的其他调控区域，ii)建立转基因模型来测试候选调控元件的功能，以及iii)对体内调控元件的dna -蛋白质相互作用进行生化表征，以确定可能在控制AICDA表达中起关键作用的候选转录因子。这一试点提案的结果将使我们能够开始研究细胞信号转导途径和转录调节因子，控制体细胞超突变和免疫球蛋白基因的类开关重组。

DESCRIPTION (provided by applicant): Immunoglobulin somatic hypermutation and class switch recombination increase the specificity and expand the functionality of the antibody repertoire in response to antigenic challenge to provide better protection against infections. Both processes involve highly ordered, temporal destabilization of the genome in mature B lymphocytes. Regulation of this genomic destabilization appears to be crucial in controlling lymphoid tumorgenesis. One important regulatory mechanism is the transcriptional control of expression of the activation-induced cytidine deaminase (AICDA) gene. AICDA provides a central catalytic activity to both hypermutation and class switch recombination, is the only known lymphoid-specific component of both processes and its transcription is predominantly restricted to germinal center B-lymphocytes. Characterization of the transcriptional control of AICDA gene expression is essential to understand the physiological regulation of hypermutation and class switch recombination and could illuminate potential pathological aberrations that lead to uncontrolled genomic instability and tumorgenesis. We have characterized the transcription of the AICDA gene in murine B-cell lines, determined the transcription start site in established cell lines and primary, splenic B-cells and identified a putative promoter of the AICDA gene which is evolutionarily conserved. In this application, we propose to perform experiments to: i) identify additional regulatory regions within the AICDA locus, ii) establish transgenic models to test the function of candidate regulatory elements, and iii) perform biochemical characterization of DNA-protein interactions of the regulatory elements in vivo to identify candidate transcription factors that may be critical in the control of AICDA expression. The results of this pilot proposal will allow us to begin studies on the cellular signal transduction pathways and transcriptional regulatory factors that control somatic hypermutation and class switch recombination of immunoglobulin genes.