Molecular architecture of the human U4/U6.U5 tri-snRNP

Science. 2016 Mar 25;351(6280):1416-20. doi: 10.1126/science.aad2085.

Dmitry E Agafonov ¹, Berthold Kastner ¹, Olexandr Dybkov ¹, Romina V Hofele ², Wen-Ti Liu ³, Henning Urlaub ⁴, Reinhard Lührmann ⁵, Holger Stark ⁶

Affiliations

1 Department of Cellular Biochemistry, Max Planck Institute for Biophysical Chemistry, D-37077 Göttingen, Germany.
2 Bioanalytical Mass Spectrometry, Max Planck Institute for Biophysical Chemistry, D-37077 Göttingen, Germany. Bioanalytics Group, Institute for Clinical Chemistry, University Medical Center Göttingen, D-37075 Göttingen, Germany.
3 Department of 3D Electron Cryomicroscopy, Georg-August Universität Göttingen, D-37077 Göttingen, Germany. Department of Structural Dynamics, Max Planck Institute for Biophysical Chemistry, D-37077 Göttingen, Germany.
4 Bioanalytical Mass Spectrometry, Max Planck Institute for Biophysical Chemistry, D-37077 Göttingen, Germany. Bioanalytics Group, Institute for Clinical Chemistry, University Medical Center Göttingen, D-37075 Göttingen, Germany. reinhard.luehrmann@mpi-bpc.mpg.de hstark1@gwdg.de henning.urlaub@mpibpc.mpg.de.
5 Department of Cellular Biochemistry, Max Planck Institute for Biophysical Chemistry, D-37077 Göttingen, Germany. reinhard.luehrmann@mpi-bpc.mpg.de hstark1@gwdg.de henning.urlaub@mpibpc.mpg.de.
6 Department of 3D Electron Cryomicroscopy, Georg-August Universität Göttingen, D-37077 Göttingen, Germany. Department of Structural Dynamics, Max Planck Institute for Biophysical Chemistry, D-37077 Göttingen, Germany. reinhard.luehrmann@mpi-bpc.mpg.de hstark1@gwdg.de henning.urlaub@mpibpc.mpg.de.

PMID: 26912367 DOI: 10.1126/science.aad2085

Abstract

The U4/U6.U5 triple small nuclear ribonucleoprotein (tri-snRNP) is a major spliceosome building block. We obtained a three-dimensional structure of the 1.8-megadalton human tri-snRNP at a resolution of 7 angstroms using single-particle cryo-electron microscopy (cryo-EM). We fit all known high-resolution structures of tri-snRNP components into the EM density map and validated them by protein cross-linking. Our model reveals how the spatial organization of Brr2 RNA helicase prevents premature U4/U6 RNA unwinding in isolated human tri-snRNPs and how the ubiquitin C-terminal hydrolase-like protein Sad1 likely tethers the helicase Brr2 to its preactivation position. Comparison of our model with cryo-EM three-dimensional structures of the Saccharomyces cerevisiae tri-snRNP and Schizosaccharomyces pombe spliceosome indicates that Brr2 undergoes a marked conformational change during spliceosome activation, and that the scaffolding protein Prp8 is also rearranged to accommodate the spliceosome's catalytic RNA network.

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