U4/U6.U5 tri-snRNP 的 3.8 A 结构：对剪接体组装和催化的洞察,Science

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U4/U6.U5 tri-snRNP 的 3.8 A 结构：对剪接体组装和催化的洞察
Science ( IF 44.7 ) Pub Date : 2016-01-07 , DOI: 10.1126/science.aad6466
Ruixue Wan ₁ , Chuangye Yan ₁ , Rui Bai ₁ , Lin Wang ₁ , Min Huang ₂ , Catherine C. L. Wong ₂ , Yigong Shi ₁

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关键剪接体复合物的结构在真核生物中，当 DNA 转录为 RNA 时，初级转录物的蛋白质编码序列被称为内含子的非编码序列中断。内含子由复杂的分子机器剪接体去除。万等人。确定了一个关键亚复合体的结构，tri-SNP，它包含三个小核 RNA 和 30 多种蛋白质。通过电子显微镜以 3.8 Å 分辨率确定的结构出人意料地显示了结合在三 SNP 中的初级 RNA 转录本。进一步的分析揭示了剪接体如何组装以实现其复杂功能。科学，这个问题 p。466 一个关键的剪接体亚复合体揭示了剪接体如何组装以发挥活性。前体信使 RNA 的剪接是由称为剪接体的动态巨型复合体完成的。功能性剪接体的组装需要预先组装的 U4/U6.U5 tri-snRNP 复合物，其中包括 U5 小核核糖核蛋白 (snRNP)、U4 和 U6 小核 RNA (snRNA) 双链体以及许多蛋白质因子。在这里，我们通过单粒子电子低温显微镜以 3.8 埃的整体分辨率报告了酿酒酵母 U4/U6.U5 tri-snRNP 的三维结构。tri-snRNP 核心区域的局部分辨率达到 3.0 到 3.5 埃，可以构建精细的原子模型。我们的结构包含 U5 snRNA、广泛碱基配对的 U4/U6 snRNA 和 30 种蛋白质，包括 Prp8 和 Snu114，共 8495 个氨基酸和 263 个核苷酸，总分子量约为 1 兆道尔顿。来自 U6 snRNA 的催化核苷酸 U80 以非活性构象存在，通过与 U4 snRNA 的碱基配对相互作用而稳定，并受到 Prp3 的保护。前信使 RNA 通过与 U6 snRNA 和 U5 snRNA 的环 I 的碱基配对相互作用结合在 tri-snRNP 中。该结构与剪接体的结构一起揭示了剪接体核酶激活过程中snRNA的分子编排。

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The 3.8 A structure of the U4/U6.U5 tri-snRNP: Insights into spliceosome assembly and catalysis

Structure of a key spliceosomal complex In eukaryotes, when DNA is transcribed into RNA, the primary transcript has protein-coding sequences interrupted by noncoding sequences called introns. Introns are removed by a complex molecular machine, the spliceosome. Wan et al. determined the structure of a key subcomplex, the tri-SNP, that comprises three small nuclear RNAs and more than 30 proteins. The structure, determined by electron microscopy at 3.8 Å resolution, unexpectedly shows a primary RNA transcript bound in the tri-SNP. Further analysis revealed how the spliceosome assembles to achieve its complex functions. Science, this issue p. 466 A key spliceosomal subcomplex reveals how the spliceosome assembles for activity. Splicing of precursor messenger RNA is accomplished by a dynamic megacomplex known as the spliceosome. Assembly of a functional spliceosome requires a preassembled U4/U6.U5 tri-snRNP complex, which comprises the U5 small nuclear ribonucleoprotein (snRNP), the U4 and U6 small nuclear RNA (snRNA) duplex, and a number of protein factors. Here we report the three-dimensional structure of a Saccharomyces cerevisiae U4/U6.U5 tri-snRNP at an overall resolution of 3.8 angstroms by single-particle electron cryomicroscopy. The local resolution for the core regions of the tri-snRNP reaches 3.0 to 3.5 angstroms, allowing construction of a refined atomic model. Our structure contains U5 snRNA, the extensively base-paired U4/U6 snRNA, and 30 proteins including Prp8 and Snu114, which amount to 8495 amino acids and 263 nucleotides with a combined molecular mass of ~1 megadalton. The catalytic nucleotide U80 from U6 snRNA exists in an inactive conformation, stabilized by its base-pairing interactions with U4 snRNA and protected by Prp3. Pre-messenger RNA is bound in the tri-snRNP through base-pairing interactions with U6 snRNA and loop I of U5 snRNA. This structure, together with that of the spliceosome, reveals the molecular choreography of the snRNAs in the activation process of the spliceosomal ribozyme.

更新日期：2016-01-07

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