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

Science. 2016 Mar 25;351(6280):1416-20. doi: 10.1126/science.aad2085. Epub 2016 Feb 18.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cryoelectron Microscopy
  • Crystallography, X-Ray
  • DEAD-box RNA Helicases / chemistry
  • Enzyme Activation
  • HeLa Cells
  • Humans
  • Models, Molecular
  • Peptide Elongation Factors / chemistry
  • Protein Conformation
  • RNA Helicases / chemistry
  • RNA-Binding Proteins / chemistry
  • Ribonucleoprotein, U4-U6 Small Nuclear / chemistry*
  • Ribonucleoprotein, U5 Small Nuclear / chemistry*
  • Ribonucleoproteins, Small Nuclear / chemistry
  • Saccharomyces cerevisiae Proteins / chemistry
  • Schizosaccharomyces / metabolism
  • Ubiquitin Thiolesterase / chemistry


  • EFTUD2 protein, human
  • PRP8 protein, S cerevisiae
  • PRPF8 protein, human
  • Peptide Elongation Factors
  • RNA-Binding Proteins
  • Ribonucleoprotein, U4-U6 Small Nuclear
  • Ribonucleoprotein, U5 Small Nuclear
  • Ribonucleoproteins, Small Nuclear
  • SNRNP200 protein, human
  • Saccharomyces cerevisiae Proteins
  • TXNL4A protein, human
  • DDX23 protein, human
  • Ubiquitin Thiolesterase
  • DEAD-box RNA Helicases
  • RNA Helicases

Associated data

  • PDB/3JCR