Major conformational change in the complex SF3b upon integration into the spliceosomal U11/U12 di-snRNP as revealed by electron cryomicroscopy.
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.
Golas
Monika M
MM
Department of Cellular Biochemistry and Research Group of 3D Electron Cryomicroscopy, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, D-37077 Göttingen, Germany.
Sander
Bjoern
B
Will
Cindy L
CL
Lührmann
Reinhard
R
Stark
Holger
H
D020285:Cryoelectron Microscopy; D019281:Dimerization; D006367:HeLa Cells; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology / Q000378:metabolism; D007438:Introns / Q000235:genetics*; D046912:Multiprotein Complexes; D010750:Phosphoproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D012326:RNA Splicing; D000072260:RNA Splicing Factors; D016601:RNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017413:Ribonucleoprotein, U2 Small Nuclear / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017411:Ribonucleoproteins, Small Nuclear / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017381:Spliceosomes / Q000737:chemistry*
D007074:Immunoglobulin G; D046912:Multiprotein Complexes; D010750:Phosphoproteins; D000072260:RNA Splicing Factors; D016601:RNA-Binding Proteins; D017413:Ribonucleoprotein, U2 Small Nuclear; D017411:Ribonucleoproteins, Small Nuclear; C112491:SF3B1 protein, human; C486347:SF3B4 protein, human; C098762:U11 small nuclear ribonucleoprotein, human; C552126:U11-U12 small nuclear ribonucleoprotein; C437317:U2 small nuclear ribonucleoprotein p14