Three-dimensional structure of C complex spliceosomes by electron microscopy.
The spliceosome is a multimegadalton RNA-protein machine that removes noncoding sequences from nascent pre-mRNAs. Recruitment of the spliceosome to splice sites and subsequent splicing require a series of dynamic interactions among the spliceosome's component U snRNPs and many additional protein factors. These dynamics present several challenges for structural analyses, including purification of stable complexes to compositional homogeneity and assessment of conformational heterogeneity. We have isolated spliceosomes arrested before the second chemical step of splicing (C complex) in which U2, U5 and U6 snRNAs are stably associated. Using electron microscopy, we obtained images of C complex spliceosomes under cryogenic conditions and determined a three-dimensional structure of a core complex to a resolution of 30 A. The structure reveals a particle of dimensions 27 x 22 x 24 nm with a relatively open arrangement of three primary domains.
Howard Hughes Medical Institute, Rosenstiel Basic Medical Sciences Research Center, Department of Biochemistry, Brandeis University, 415 South Street, Waltham, Massachusetts 02454, USA. jurica@biology.ucsc.edu
Melissa S
MS
Jurica
Duncan
D
Sousa
Melissa J
MJ
Moore
Nikolaus
N
Grigorieff
D020285:Cryoelectron Microscopy / Q000379:methods*; D006367:HeLa Cells; D006801:Humans; D021621:Imaging, Three-Dimensional; D009154:Mutation; D011487:Protein Conformation; D022821:RNA Splice Sites / Q000235:genetics; D017413:Ribonucleoprotein, U2 Small Nuclear / Q000737:chemistry; D017414:Ribonucleoprotein, U4-U6 Small Nuclear / Q000737:chemistry; D017415:Ribonucleoprotein, U5 Small Nuclear / Q000737:chemistry; D017381:Spliceosomes / Q000737:chemistry*
D022821:RNA Splice Sites; D017413:Ribonucleoprotein, U2 Small Nuclear; D017414:Ribonucleoprotein, U4-U6 Small Nuclear; D017415:Ribonucleoprotein, U5 Small Nuclear