A multiprotein complex mediates the ATP-dependent assembly of spliceosomal U snRNPs

Nat Cell Biol. 2001 Nov;3(11):945-9. doi: 10.1038/ncb1101-945.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adenosine Triphosphate / metabolism*
  • Animals
  • Autoantigens / metabolism*
  • Cyclic AMP Response Element-Binding Protein
  • HeLa Cells
  • Humans
  • Nerve Tissue Proteins / metabolism*
  • Proteins / metabolism
  • RNA-Binding Proteins
  • Ribonucleoprotein, U1 Small Nuclear / metabolism*
  • Ribonucleoproteins, Small Nuclear*
  • SMN Complex Proteins
  • Spliceosomes / metabolism*
  • Xenopus laevis / metabolism
  • snRNP Core Proteins


  • Autoantigens
  • Cyclic AMP Response Element-Binding Protein
  • GEMIN2 protein, human
  • Nerve Tissue Proteins
  • Proteins
  • RNA-Binding Proteins
  • Ribonucleoprotein, U1 Small Nuclear
  • Ribonucleoproteins, Small Nuclear
  • SMN Complex Proteins
  • SNRPN protein, human
  • snRNP Core Proteins
  • Adenosine Triphosphate