前mRNA剪接是真核生物基因表达调控的主要过程,可变剪接用于从相同的编码基因产生不同的蛋白质。剪接是一种催化过程,它去除内含子并连接外显子以产生编码最终蛋白质的RNA序列。虽然这是在原核生物的祖先II型内含子中的自催化过程中实现的,剪接体在真核发生过程中进化,以协助这一过程,并最终为内含子特异性剪接提供机会。在拼接的早期阶段,必须将RNA5'和3'剪接位点带到附近,以正确组装活性剪接体并进行切除和连接反应。第一个建筑群的组装,被称为E-复合体,是目前最不了解的过程。在这篇综述中,我们重点关注了E复合物的形成,并比较了其在三种不同生物中的组成和功能。我们强调了酿酒酵母中常见的祖先机制,S、庞贝,和哺乳动物,并以组成型和受调控的共转录剪接中内含子定义的统一模型得出结论。
Pre-mRNA splicing is a major process in the regulated expression of genes in eukaryotes, and alternative splicing is used to generate different proteins from the same coding gene. Splicing is a catalytic process that removes introns and ligates exons to create the RNA sequence that codifies the final protein. While this is achieved in an autocatalytic process in ancestral group II introns in prokaryotes, the spliceosome has evolved during eukaryogenesis to assist in this process and to finally provide the opportunity for intron-specific splicing. In the early stage of splicing, the RNA 5\' and 3\' splice sites must be brought within proximity to correctly assemble the active spliceosome and perform the excision and ligation reactions. The assembly of this first complex, termed E-complex, is currently the least understood process. We focused in this review on the formation of the E-complex and compared its composition and function in three different organisms. We highlight the common ancestral mechanisms in S. cerevisiae, S. pombe, and mammals and conclude with a unifying model for intron definition in constitutive and regulated co-transcriptional splicing.