MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom.
Cold Spring Harb Perspect Biol. 2019 May 1;11(5):a032391. doi: 10.1101/cshperspect.a032391.
Noncoding introns are removed from nuclear precursor messenger RNA (pre-mRNA) in a two-step phosphoryl transfer reaction by the spliceosome, a dynamic multimegadalton enzyme. Cryo-electron microscopy (cryo-EM) structures of the spliceosome were recently determined in eight key states. Combined with the wealth of available genetic and biochemical data, these structures have revealed new insights into the mechanisms of spliceosome assembly, activation, catalysis, and disassembly. The structures show how a single RNA catalytic center forms during activation and accomplishes both steps of the splicing reaction. The structures reveal how spliceosomal helicases remodel the spliceosome for active site formation, substrate docking, reaction product undocking, and spliceosome disassembly and how they facilitate splice site proofreading. Although human spliceosomes contain additional proteins, their cryo-EM structures suggest that the underlying mechanism is conserved across all eukaryotes. In this review, we summarize the current structural understanding of pre-mRNA splicing.
非编码内含子通过剪接体（一种动态的兆道尔顿酶）在两步磷酸转移反应中从核前体信使 RNA（pre-mRNA）中被切除。剪接体的冷冻电镜（cryo-EM）结构最近在八个关键状态下被确定。结合丰富的可用遗传和生化数据，这些结构揭示了剪接体组装、激活、催化和解体机制的新见解。这些结构展示了单个 RNA 催化中心如何在激活过程中形成，并完成剪接反应的两个步骤。这些结构揭示了剪接体解旋酶如何重塑剪接体以形成活性位点、底物对接、反应产物卸接以及剪接体解体，以及它们如何促进剪接位点校对。尽管人类剪接体包含额外的蛋白质，但它们的 cryo-EM 结构表明，基本机制在所有真核生物中都是保守的。在这篇综述中，我们总结了 pre-mRNA 剪接的当前结构理解。
