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Ubiquitin binding by a variant Jab1/MPN domain in the essential pre-mRNA splicing factor Prp8p.

The U1, U2, U4/U6, and U5 small nuclear ribonucleoproteins (snRNPs) are components of the spliceosome, which catalyzes pre-mRNA splicing. One of the largest and the most highly conserved proteins in the spliceosome is Prp8p, a component of the U5 snRNP. Despite its size and conservation, very few motifs have been identified that suggest specific biochemical functions. A variant of the Jab1/MPN domain found in a class of deubiquitinating enzymes is present near the C terminus of Prp8p. Ubiquitination regulates a broad range of cellular pathways, and its functions generally require ubiquitin recognition by one or more ubiquitin-binding domains (UBDs). No precise role for ubiquitin has been defined in the pre-mRNA splicing pathway, and no known UBDs have been found within splicing proteins. Here we show that a Prp8p fragment containing the Jab1/MPN domain binds directly to ubiquitin with an affinity comparable to other known UBDs. Several mutations within this domain that compromise splicing also reduce interaction of the fragment with ubiquitin-Sepharose. Our results define a new UBD and suggest functional links between ubiquitin and the pre-mRNA splicing machinery.

Pubmed ID: 16428608


  • Bellare P
  • Kutach AK
  • Rines AK
  • Guthrie C
  • Sontheimer EJ


RNA (New York, N.Y.)

Publication Data

February 23, 2006

Associated Grants

  • Agency: NIGMS NIH HHS, Id: GM21119

Mesh Terms

  • Amino Acid Motifs
  • Amino Acid Sequence
  • Binding Sites
  • Gene Expression Regulation, Fungal
  • Metalloendopeptidases
  • Molecular Sequence Data
  • Mutation
  • Protein Structure, Tertiary
  • RNA Precursors
  • RNA Splicing
  • Ribonucleoprotein, U4-U6 Small Nuclear
  • Ribonucleoprotein, U5 Small Nuclear
  • Saccharomyces cerevisiae Proteins
  • Sequence Homology, Amino Acid
  • Ubiquitin