Understanding the mechanism of pre-mRNA splicing

项目总结 剪接是前信使核糖核酸加工的重要步骤，在此过程中内含子被切除，外显子被连接。 这是由剪接体催化的，剪接体识别剪接位点(Ss)并在其前-mrna上组装。 以一种循序渐进的方式衬底。剪接体经历了多次重排，主要是由 DExD/H-box螺旋酶，在剪接循环中。基因的剪接位点识别和结构重排 剪接体需要高保真地进行。拼接错误约占人类总数的30% 遗传性疾病和包括癌症在内的许多其他疾病的发展。 尽管经过了几十年的研究，最初剪接位点识别的机制在很大程度上仍然是一个谜。那里 目前对SS的识别有两种模型，即内含子和外显子定义。在前一种模式中， 剪接体最初识别和组装内含子，然后内含子被切除，连接侧翼 外显子。在后一种模式中，剪接体首先围绕一个外显子组装，然后被改造成一个交叉的- 内含子复合体，然后拼接出内含子。目前尚不清楚复合体是跨外显子组装还是跨外显子组装 内含子是相同的还是不同的，以及外显子定义重塑到底是如何发生的。我们的实验室 最近确定了酵母菌的E-复合体结构。这种结构表明，完全相同的剪接体 可以在外显子上组装并进行外显子定义，而不需要额外的组件或结构 重新安排。为了为这一假说提供第一个实验证据，我们将解决一个 早期剪接体复合体在一个内含子和一个外显子上组装。这个项目的结果将是 显著提高了我们对剪接体识别初始内含子/外显子的理解。 DExD/H-box解旋酶在驱动剪接体转变和所有四种Deah-box剪接体中都是重要的 参与晚期剪接的解旋酶(Prp2、Prp16、Prp22和Prp43)具有有趣的结构相似性。在……里面 尽管对这些解旋酶进行了广泛的生化和结构分析，但还不清楚是什么结构成分 在Deah-box中，解旋酶负责解旋酶的活性。目前也不清楚它们是如何具体 被招募到剪接体，并被监管在正确的时间和地点执行其专门的动作。我瞄准了 为了解决这些问题，使用Prp22作为模型，主要采用生物化学方法。这些结果可能 为所有四种Deah-box剪接体螺旋酶的机制和调控提供重要的见解。

PROJECT SUMMARY Splicing is an essential step in pre-mRNA processing during which introns are excised, and exons are ligated. This is catalyzed by the spliceosome which recognizes splice sites (ss) and assembles on its pre-mRNA substrate in a stepwise manner. The spliceosome undergoes multiple rearrangements, largely driven by DExD/H-box helicases, during the splicing cycle. Splice site recognition and structural rearrangement of the spliceosome need to be carried out with high fidelity. Errors in splicing contribute to around 30% of human genetic disorders and the development of many other diseases including cancer. In spite of decades of research, the mechanism of initial splice site recognition is still largely a mystery. There are currently two models for ss recognition, namely intron and exon definition. In the former model, the spliceosome initially recognizes and assembles across introns which is then excised, ligating the flanking exons. In the latter model, the spliceosome first assembles around an exon and is remodeled into a cross- intron complex before splicing out the intron. It is unclear whether complexes assembled across an exon or an intron are the same or different from each other, and how exactly exon definition remodeling occurs. Our lab recently determined the yeast E-complex structure. The structure suggest that the exact same spliceosome can assemble on an exon and carry out exon definition without the need of additional components or structural rearrangements. To provide the first experimental evidence for this hypothesis, we will solve the structure of an early spliceosomal complex assembled on both an intron and an exon. Results from this project will significantly advance our understanding of initial intron/exon recognition by the spliceosome. DExD/H-box helicases are important in driving spliceosome transitions and all four DEAH-box spliceosomal helicases (Prp2, Prp16, Prp22 and Prp43) involved in late splicing share intriguing structural similarities. In spite of extensive biochemical and structural analyses of these helicases, it is unclear what structural element in DEAH-box helicases is responsible for the helicase activity. It is also unclear how they are specifically recruited to the spliceosome and regulated to perform their dedicated action at the right time and place. I aim to address these questions using Prp22 as a model with mostly biochemical approaches. These results may provide important insights into the mechanism and regulation of all four DEAH-box spliceosomal helicases.