title: Ubiquitin binding by a variant Jab1/MPN domain in the essential pre-mRNA splicing factor Prp8p.
abstract: 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.
authors.affiliation: Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, 2205 Tech Drive, Evanston, IL 60208, USA.
authors.forename: Priya
authors.initials: P
authors.lastname: Bellare
authors.forename: Alan K
authors.initials: AK
authors.lastname: Kutach
authors.forename: Amy K
authors.initials: AK
authors.lastname: Rines
authors.forename: Christine
authors.initials: C
authors.lastname: Guthrie
authors.forename: Erik J
authors.initials: EJ
authors.lastname: Sontheimer
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001665:Binding Sites; D000075686:COP9 Signalosome Complex; D015966:Gene Expression Regulation, Fungal; D008666:Metalloendopeptidases / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D017434:Protein Structure, Tertiary; D012322:RNA Precursors / Q000235:genetics / Q000378:metabolism; D012326:RNA Splicing; D017414:Ribonucleoprotein, U4-U6 Small Nuclear; D017415:Ribonucleoprotein, U5 Small Nuclear / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D025801:Ubiquitin / Q000378:metabolism*
chemical_list: C077018:PRP8 protein, S cerevisiae; D012322:RNA Precursors; D017414:Ribonucleoprotein, U4-U6 Small Nuclear; D017415:Ribonucleoprotein, U5 Small Nuclear; D029701:Saccharomyces cerevisiae Proteins; D025801:Ubiquitin; D000075686:COP9 Signalosome Complex; D008666:Metalloendopeptidases; C468276:Rri1 protein, S cerevisiae