REGULATION OF IGH MU LOCUS CLASS SWITCH RECOMBINATION

描述（研究者摘要）：在体液免疫应答期间， 免疫球蛋白（IG）类别转换改变了免疫球蛋白的效应功能。 抗体，而不改变其对抗原的特异性，通过取代重链， u基因的链恒定区（CH）序列与γ基因的序列， α基因。这是通过DNA序列的重组完成的 （S区域）Cu和“下游”CH基因的5'。按照目前的 模型，响应于特定B的类别转换重组（CSR）的调节 细胞刺激是通过调节转录活性来实现的。 靶向CH基因以产生所谓的“生殖系”（或“开关”）转录物。 u基因座在类别转换中起着特别重要的作用，因为Su是 每一次CSR活动的义务捐助者。然而，目前的企业社会责任模式 监管不能令人满意地解释企业社会责任活动的所有特征， 由于u基因座转换转录物在整个B细胞中表达 在没有可检测的CSR活性的情况下发展。此外，删除 U开关转录物的已知调节和结构元件具有 仅对u CSR有部分影响。在一系列的实验中， 观察，我们最近发现了新的u位点转录单位 可能涉及CSR监管。利用这个新的 信息，我们在这里提出了一系列的实验，旨在阐明 影响u位点CSR的调节机制。具体来说，我们将 表征调节新转录物表达的元件，和 通过靶向诱变评估它们的功能。测试生成和 正如最近提出的，u开关转录本的剪接对于CSR是必需的 对于其他CH基因，我们将替换整个u开关转录本， 含有外源DNA序列的区域。在转基因实验中，我们将检测 顺式和反式调节机制在控制Su 重组最后，通过用不同类型的 序列（重复和非重复，S相关或不相关），我们将建立 Su区序列作为有效CSR的分子要求 印刷受体.

DESCRIPTION (investigator's abstract): During a humoral immune response, immunoglobulin (Ig) class switching changes the effector function of an antibody, without altering its specificity for antigen, by replacing the heavy chain constant region (CH) sequences of the u gene with those of a gamma, epsilon or alpha gene. This is accomplished via recombination of DNA sequences (S regions) 5' of Cu and of the "downstream" CH genes. According to the current model, regulation of class switch recombination (CSR) in response to specific B cell stimuli is achieved by modulation of the transcriptional activity of the target CH genes to generate so-called "germline" (or "switch") transcripts. The u locus plays a particularly important role in class switching, since Su is the obligate donor of every CSR event. Yet, the present models of CSR regulation do not satisfactorily explain all the features of u CSR activity, since the u locus switch transcripts are expressed throughout B cell development in the absence of detectable CSR activity. Moreover, deletions of the known regulatory and structural elements of the u switch transcripts have only a partial effect on u CSR. In a series of experiments stemming from these observations, we have recently identified novel u locus transcription units that may be involved in CSR regulation. Taking advantage of this new information, we propose here a series of experiments aimed at elucidating the regulatory mechanisms that affect CSR at the u locus. Specifically, we will characterize the elements that regulate expression of the new transcripts, and assess their function by targeted mutagenesis. To test whether generation and splicing of u switch transcripts is essential for CSR, as recently suggested for other CH genes, we are going to replace the entire u switch transcript region with exogenous DNA sequences. In transgenic experiments, we will assay for the role of cis- and trans-acting regulatory mechanisms in controlling Su recombination. Finally, by replacing the endogenous Su with different types of sequences (repetitive and non-repetitive, S-related or not) we will establish the molecular requirements for the Su region sequences as efficient CSR substrates.