Pre-mRNA splicing, a fundamental step in eukaryotic gene expression, is executed by the spliceosomes. While there is extensive knowledge of the composition and structure of spliceosomes in yeasts and humans, the structural diversity of spliceosomes in non-canonical organisms remains unclear. Here, we present a cryo-EM structure of a step II catalytically activated spliceosome (C* complex) derived from the unicellular green alga Chlamydomonas reinhardtii at 2.6 Å resolution. This Chlamydomonas C* complex comprises 29 proteins and four RNA elements, creating a dynamic assembly that shares a similar overall architecture with yeast and human counterparts but also has unique features of its own. Distinctive structural characteristics include variations in protein compositions as well as some noteworthy RNA features. The splicing factor Prp17, with four fragments and a WD40 domain, is engaged in intricate interactions with multiple protein and RNA components. The structural elucidation of Chlamydomonas C* complex provides insights into the molecular mechanism of RNA splicing in plants and understanding splicing evolution in eukaryotes.

中文翻译：

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来自 Chlamydomonas reinhardtii 的第二步催化激活剪接体的结构。


前 mRNA 剪接是真核基因表达的基本步骤，由剪接体执行。虽然对酵母和人类剪接体的组成和结构有广泛的了解，但非经典生物体中剪接体的结构多样性仍不清楚。在这里，我们以 2.6 Å 的分辨率展示了源自单细胞绿藻莱茵衣藻的第 II 步催化激活剪接体 （C* 复合物） 的冷冻电镜结构。这种衣藻 C* 复合物由 29 种蛋白质和 4 种 RNA 元件组成，形成了一个动态组装体，该组装体与酵母和人类相似的整体结构相似，但也具有自己的独特功能。独特的结构特征包括蛋白质组成的变化以及一些值得注意的 RNA 特征。剪接因子 Prp17 具有四个片段和一个 WD40 结构域，与多种蛋白质和 RNA 组分进行复杂的相互作用。衣藻 C* 复合物的结构解析为植物中 RNA 剪接的分子机制和真核生物剪接进化提供了见解。