Molecular architecture of the human U4/U6.U5 tri-snRNP.Agafonov, D.E., Kastner, B., Dybkov, O., Hofele, R.V., Liu, W.T., Urlaub, H., Luhrmann, R., Stark, H.
(2016) Science 351: 1416-1420
- PubMed: 26912367
- DOI: https://doi.org/10.1126/science.aad2085
- Primary Citation of Related Structures:
- PubMed 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.
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.