Functional interaction of a novel 15.5kD [U4/U6.U5] tri-snRNP protein with the 5' stem-loop of U4 snRNA

EMBO J. 1999 Nov 1;18(21):6119-33. doi: 10.1093/emboj/18.21.6119.


Activation of the spliceosome for splicing catalysis requires the dissociation of U4 snRNA from the U4/U6 snRNA duplex prior to the first step of splicing. We characterize an evolutionarily conserved 15.5 kDa protein of the HeLa [U4/U6.U5] tri-snRNP that binds directly to the 5' stem-loop of U4 snRNA. This protein shares a novel RNA recognition motif with several RNP-associated proteins, which is essential, but not sufficient for RNA binding. The 15.5kD protein binding site on the U4 snRNA consists of an internal purine-rich loop flanked by the stem of the 5' stem-loop and a stem comprising two base pairs. Addition of an RNA oligonucleotide comprising the 5' stem-loop of U4 snRNA (U4SL) to an in vitro splicing reaction blocked the first step of pre-mRNA splicing. Interestingly, spliceosomal C complex formation was inhibited while B complexes accumulated. This indicates that the 15.5kD protein, and/or additional U4 snRNP proteins associated with it, play an important role in the late stage of spliceosome assembly, prior to step I of splicing catalysis. Our finding that the 15.5kD protein also efficiently binds to the 5' stem-loop of U4atac snRNA indicates that it may be shared by the [U4atac/U6atac.U5] tri-snRNP of the minor U12-type spliceosome.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • Binding Sites
  • Cloning, Molecular
  • Conserved Sequence
  • HeLa Cells
  • Humans
  • Molecular Sequence Data
  • Mutation
  • Nucleic Acid Conformation
  • Phylogeny
  • RNA Precursors / genetics
  • RNA Splicing
  • RNA, Small Nuclear / metabolism*
  • RNA-Binding Proteins / chemistry
  • RNA-Binding Proteins / genetics
  • Ribonucleoproteins, Small Nuclear / chemistry
  • Ribonucleoproteins, Small Nuclear / genetics*
  • Sequence Alignment
  • Spliceosomes / metabolism


  • RNA Precursors
  • RNA, Small Nuclear
  • RNA-Binding Proteins
  • Ribonucleoproteins, Small Nuclear
  • Snu13 protein, human

Associated data

  • GENBANK/AF155235