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Chari, A., Golas, M.M., Klingenh´┐Żger, M., Neuenkirchen, N., Sander, B., Englbrecht, C., Sickmann, A., Stark, H., Fischer, U. (2008). An assembly chaperone collaborates with the SMN complex to generate spliceosomal SnRNPs.  Cell 135(3): 497--509.
FlyBase ID
FBrf0218721
Publication Type
Research paper
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.

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    Language of Publication
    English
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    Parent Publication
    Publication Type
    Journal
    Abbreviation
    Cell
    Title
    Cell
    Publication Year
    1974-
    ISBN/ISSN
    0092-8674
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