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An assembly chaperone collaborates with the SMN complex to generate spliceosomal SnRNPs.
- Source :
-
Cell [Cell] 2008 Oct 31; Vol. 135 (3), pp. 497-509. - Publication Year :
- 2008
-
Abstract
- Spliceosomal small nuclear ribonucleoproteins (snRNPs) are essential components of the nuclear pre-mRNA processing machinery. A hallmark of these particles is a ring-shaped core domain generated by the binding of Sm proteins onto snRNA. PRMT5 and SMN complexes mediate the formation of the core domain in vivo. Here, we have elucidated the mechanism of this reaction by both biochemical and structural studies. We show that pICln, a component of the PRMT5 complex, induces the formation of an otherwise unstable higher-order Sm protein unit. In this state, the Sm proteins are kinetically trapped, preventing their association with snRNA. The SMN complex subsequently binds to these Sm protein units, dissociates pICln, and catalyzes ring closure on snRNA. Our data identify pICln as an assembly chaperone and the SMN complex as a catalyst of spliceosomal snRNP formation. The mode of action of this combined chaperone/catalyst system is reminiscent of the mechanism employed by DNA clamp loaders.
- Subjects :
- HeLa Cells
Humans
Models, Biological
Molecular Chaperones metabolism
Nerve Tissue Proteins metabolism
Protein Methyltransferases metabolism
Protein-Arginine N-Methyltransferases
RNA metabolism
RNA-Binding Proteins metabolism
Ribonucleoproteins, Small Nuclear chemistry
Survival of Motor Neuron 1 Protein metabolism
Protein Methyltransferases chemistry
Ribonucleoproteins, Small Nuclear metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 1097-4172
- Volume :
- 135
- Issue :
- 3
- Database :
- MEDLINE
- Journal :
- Cell
- Publication Type :
- Academic Journal
- Accession number :
- 18984161
- Full Text :
- https://doi.org/10.1016/j.cell.2008.09.020