Major conformational change in the complex SF3b upon integration into the spliceosomal U11/U12 di-snRNP as revealed by electron cryomicroscopy

Mol Cell. 2005 Mar 18;17(6):869-83. doi: 10.1016/j.molcel.2005.02.016.

Abstract

In some eukaryotes, a minor class of introns is removed by the U12-dependent spliceosome, which contains the small nuclear ribonucleoprotein (snRNP) heterodimer U11/U12. The U11/U12 di-snRNP forms a molecular bridge that functionally pairs the intron ends of the pre-mRNA. We have determined the three-dimensional (3D) structure of the human U11/U12 di-snRNP by single particle electron cryomicroscopy using angular reconstitution and random conical tilt. SF3b, a heteromeric protein complex functionally important for branch site recognition, was located in the U11/U12 di-snRNP by antibody labeling and by identification of structural domains of SF3b155, SF3b49, and p14. The conformation of SF3b bound to the U11/U12 di-snRNP differs from that of isolated SF3b: upon integration into the di-snRNP, SF3b rearranges into a more open form. The manner in which SF3b is integrated in the U11/U12 di-snRNP has important implications for branch site recognition. Furthermore, a putative model of the pre-mRNA binding to the U11/U12 di-snRNP is proposed.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cryoelectron Microscopy
  • Dimerization
  • HeLa Cells
  • Humans
  • Immunoglobulin G / immunology
  • Immunoglobulin G / metabolism
  • Introns / genetics*
  • Multiprotein Complexes
  • Phosphoproteins / chemistry*
  • Phosphoproteins / genetics
  • Phosphoproteins / metabolism
  • Protein Conformation*
  • RNA Splicing
  • RNA Splicing Factors
  • RNA-Binding Proteins / chemistry*
  • RNA-Binding Proteins / genetics
  • RNA-Binding Proteins / metabolism
  • Ribonucleoprotein, U2 Small Nuclear / chemistry*
  • Ribonucleoprotein, U2 Small Nuclear / genetics
  • Ribonucleoprotein, U2 Small Nuclear / metabolism
  • Ribonucleoproteins, Small Nuclear / chemistry*
  • Ribonucleoproteins, Small Nuclear / genetics
  • Ribonucleoproteins, Small Nuclear / metabolism
  • Spliceosomes / chemistry*

Substances

  • Immunoglobulin G
  • Multiprotein Complexes
  • Phosphoproteins
  • RNA Splicing Factors
  • RNA-Binding Proteins
  • Ribonucleoprotein, U2 Small Nuclear
  • Ribonucleoproteins, Small Nuclear
  • SF3B1 protein, human
  • SF3B4 protein, human
  • U11 small nuclear ribonucleoprotein, human
  • U11-U12 small nuclear ribonucleoprotein
  • U2 small nuclear ribonucleoprotein p14