mRNA alternative polyadenylation in B cell development

项目总结： 绝大多数哺乳动物的基因通过产生交替加工的mRNAs 选择性剪接和选择性聚腺苷酸化(APA)。产生不同的信使核糖核酸亚型 可以编码不同的蛋白质和/或它们可能受到不同的调控。 最近的研究揭示了信使核糖核酸的选择性加工在许多生物中的重要作用。 选择性剪接和APA的过程和错误调控与广泛的 一系列疾病，包括癌症和神经退行性疾病。然而，这种机制 B组的抗体分泌功能仍未得到很好的了解 细胞是我们免疫反应和错误调节的抗体反应的主要组成部分。 是许多自身免疫性疾病的基础。B细胞的激活和分化需要复杂的 基因调控级联反应。以前的工作，包括我们的工作，已经提供了对 调控这一过程的转录调控机制。然而，很明显，邮政- 转录基因调控，如选择性剪接和APA，也起着重要作用。 1980年，几项里程碑式的研究报告了第一个替代RNA加工的例子： 免疫球蛋白M(IgM)重链基因(IghM)产生两种APA亚型，编码a 膜结合型和分泌型。此外，IghM APA还在开发中 受监管的。然而，随后的研究未能提供一个一致的机制模型。 用于此APA交换机。此外，尚不清楚《行政程序法》的规定有多广泛 网络是什么以及APA调节在B细胞激活和 差异化。在我们的初步研究中，我们提供了证据，证明转录因子，核心 MRNA 3‘加工因子和RNA结合蛋白调节IghM APA。此外，我们 发现B细胞的激活导致~900个基因的APA模式发生显著变化， 包括编码关键细胞命运调节蛋白和信号蛋白的那些。基于这些 初步结果，我们假设IghM的APA和一个大的基因网络受到调控 APA的调节在B细胞功能中起着重要作用。为了测试这些 假设，我们设计了以下具体目标：1)确定B细胞的调节因子 用生化和遗传方法激活诱导的IghM APA开关；2)系统地 研究B细胞活化诱导IghM APA转换的机制；3)确定其作用 APA在B细胞活化和分化中的调节作用。圆满完成拟议中的 研究将为APA的调节和功能提供基本的见解。更重要的是，我们的 结果将揭示转录后基因调控在B细胞发育和B细胞- 介导的免疫反应，这将为开发疫苗的更好战略铺平道路 以及自身免疫性疾病的治疗。

Project summary: The vast majority of mammalian genes produce alternatively processed mRNAs through alternative splicing and alternative polyadenylation (APA). Different mRNA isoforms produced from the same gene can encode distinct proteins and/or they may be differentially regulated. Recent studies have revealed essential roles of mRNA alternative processing in many biological processes and mis-regulation of alternative splicing and APA has been causally linked to a wide range of diseases, including cancer and neurodegenerative diseases. However, the mechanism and functions of alternative mRNA processing remain poorly understood.Antibody secretion by B cells is a major component of our immune response and mis-regulated antibody response underlies many auto-immune diseases. B cell activation and differentiation require a sophisticated gene regulation cascade. Previous works, including ours, have provided insights into the transcriptional regulation mechanisms governing this process. However, it is clear that post- transcriptional gene regulation, such as alternative splicing and APA, also play an important role. In 1980, several landmark studies reported the first example of alternative RNA processing: the Immunoglobulin M (IgM) heavy chain gene (IghM) produces two APA isoforms, which encode a membrane-bound and a secreted IgM respectively. Additionally the IghM APA is developmentally regulated. Subsequent studies, however, have failed to provide a consistent mechanistic model for this APA switch. Furthermore, it remains unknown how widespread the APA regulation network is and what the functional impact of APA regulation is during B cell activation and differentiation. In our preliminary studies, we provided evidence that transcription factors, core mRNA 3’ processing factors, and RNA-binding proteins regulate IghM APA. In addition, we discovered that B cell activation leads to a significantly change in the APA patterns of ~900 genes, including those encoding key cell fate regulators and signaling proteins. Based on these preliminary results, we hypothesize that the APA of IghM and a large gene network are regulated at multiple levels and that APA regulation plays an important role in B cell functions. To test these hypotheses, we have designed the following specific aims: 1) Identify regulators of B cell activation-induced IghM APA switch using a biochemical and genetic approach; 2) Systematically characterize the mechanisms of B cell activation-induced IghM APA switch; 3) Determine the role of APA regulation in B cell activation and differentiation. Successful completion of the proposed studies will provide fundamental insights into APA regulation and function. More importantly, our results will reveal the role of post-transcriptional gene regulation in B cell development and B cell- mediated immune response, which will pave the way for better strategies for developing vaccines and treatment for autoimmune diseases.