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Updated: Aug 3, 2026

Complementation of Splicing Activity by a Galectin-3 - U1 snRNP Complex on Beads
Published on: December 9, 2020
A multiprotein complex mediates the ATP-dependent assembly of spliceosomal U snRNPs
G Meister1, D Bühler, R Pillai
1Max-Planck Institute of Biochemistry, Am Klopferspitz 18a, D-82152 Martinsried, Germany.
Abstract:
The spliceosomal snRNPs U1, U2, U4 and U5 contain a common RNP structure termed the Sm core that is formed by the binding of Sm proteins onto the U snRNA. Although isolated Sm proteins assemble spontaneously onto U snRNAs in vitro, there is increasing evidence that SMN and its interactor Gemin2 are involved in this process in vivo. Here, we describe a cell-free assay system for the assembly of U snRNPs that closely reproduces in vivo conditions. Using this system, we show that assembly of U1 snRNP depends on ATP. Immunodepletion of SMN-Gemin2 from the extract abolished assembly even though the extract contained high levels of Sm proteins. An affinity-purified macromolecular SMN complex consisting of 16 components including all Sm proteins restored assembly in the immunodepleted extract. These data provide the first direct evidence that a complex containing SMN and Gemin2 mediates the active assembly of spliceosomal U snRNPs.
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