title: A novel U2 and U11/U12 snRNP protein that associates with the pre-mRNA branch site.
abstract: Previous UV cross-linking studies demonstrated that, upon integration of the U2 snRNP into the spliceosome, a 14 kDa protein (p14) interacts directly with the branch adenosine, the nucleophile for the first transesterification step of splicing. We have identified the cDNA encoding this protein by microsequencing a 14 kDa protein isolated from U2-type spliceosomes. This protein contains an RNA recognition motif and is highly conserved across species. Antibodies raised against this cDNA-encoded protein precipitated the 14 kDa protein cross-linked to the branch adenosine, confirming the identity of the p14 cDNA. A combination of immunoblotting, protein microsequencing and immunoprecipitation revealed that p14 is a component of both 17S U2 and 18S U11/U12 snRNPs, suggesting that it contributes to the interaction of these snRNPs with the branch sites of U2- and U12-type pre-mRNAs, respectively. p14 was also shown to be a subunit of the heteromeric splicing factor SF3b and to interact directly with SF3b155. Immuno precipitations indicated that p14 is present in U12-type spliceosomes, consistent with the idea that branch point selection is similar in the major and minor spliceosomes.
authors.affiliation: Department of Cellular Biochemistry, Max Planck Institute of Biophysical Chemistry, D-37077 Göttingen, EMBL, Protein and Peptide Group, D-69117 Heidelberg, Germany. cwill1@gwdg.de
authors.forename: C L
authors.initials: CL
authors.lastname: Will
authors.forename: C
authors.initials: C
authors.lastname: Schneider
authors.forename: A M
authors.initials: AM
authors.lastname: MacMillan
authors.forename: N F
authors.initials: NF
authors.lastname: Katopodis
authors.forename: G
authors.initials: G
authors.lastname: Neubauer
authors.forename: M
authors.initials: M
authors.lastname: Wilm
authors.forename: R
authors.initials: R
authors.lastname: Lührmann
authors.forename: C C
authors.initials: CC
authors.lastname: Query
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D003001:Cloning, Molecular; D017124:Conserved Sequence; D003432:Cross-Linking Reagents; D019143:Evolution, Molecular; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D010455:Peptides / Q000145:classification / Q000235:genetics / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism*; D012322:RNA Precursors / Q000378:metabolism*; D012326:RNA Splicing; D000072260:RNA Splicing Factors; D016601:RNA-Binding Proteins / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D017413:Ribonucleoprotein, U2 Small Nuclear / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D017411:Ribonucleoproteins, Small Nuclear / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D017381:Spliceosomes / Q000378:metabolism
chemical_list: D003432:Cross-Linking Reagents; D010455:Peptides; D010750:Phosphoproteins; D012322:RNA Precursors; D000072260:RNA Splicing Factors; D016601:RNA-Binding Proteins; D017413:Ribonucleoprotein, U2 Small Nuclear; D017411:Ribonucleoproteins, Small Nuclear; C112491:SF3B1 protein, human; C098762:U11 small nuclear ribonucleoprotein, human; C552126:U11-U12 small nuclear ribonucleoprotein; C437317:U2 small nuclear ribonucleoprotein p14