Department of Structural Dynamics, MPI for Biophysical Chemistry, Am Fassberg 11, D-37077 Göttingen, Germany.
Department of Cellular Biochemistry, MPI for Biophysical Chemistry, Am Fassberg 11, D-37077 Göttingen, Germany.
Nature. 2017 Feb 16;542(7641):318-323. doi: 10.1038/nature21079. Epub 2017 Jan 11.
Spliceosome rearrangements facilitated by RNA helicase PRP16 before catalytic step two of splicing are poorly understood. Here we report a 3D cryo-electron microscopy structure of the human spliceosomal C complex stalled directly after PRP16 action (C*). The architecture of the catalytic U2-U6 ribonucleoprotein (RNP) core of the human C* spliceosome is very similar to that of the yeast pre-Prp16 C complex. However, in C* the branched intron region is separated from the catalytic centre by approximately 20 Å, and its position close to the U6 small nuclear RNA ACAGA box is stabilized by interactions with the PRP8 RNase H-like and PRP17 WD40 domains. RNA helicase PRP22 is located about 100 Å from the catalytic centre, suggesting that it destabilizes the spliced mRNA after step two from a distance. Comparison of the structure of the yeast C and human C* complexes reveals numerous RNP rearrangements that are likely to be facilitated by PRP16, including a large-scale movement of the U2 small nuclear RNP.
RNA 解旋酶 PRP16 在剪接的催化步骤二之前促进剪接体重排，但这一过程的细节仍不清楚。本文报道了人类剪接体 C 复合物在 PRP16 作用后直接停滞（C*）的三维冷冻电镜结构。人类 C剪接体的催化 U2-U6 核糖核蛋白（RNP）核心的结构与酵母前 Prp16 C 复合物非常相似。然而，在 C中，分支的内含子区域与催化中心分离约 20Å，其靠近 U6 小核 RNA ACAGA 盒的位置通过与 PRP8 RNase H 样和 PRP17 WD40 结构域的相互作用而稳定。RNA 解旋酶 PRP22 位于催化中心约 100Å 处，表明它可能通过远距离作用于第二步之后使剪接的 mRNA 不稳定。对酵母 C 和人类 C*复合物结构的比较揭示了许多可能由 PRP16 促进的 RNP 重排，包括 U2 小核 RNP 的大规模运动。
