title: U snRNP assembly in yeast involves the La protein.
abstract: In all eukaryotic nuclei, the La autoantigen binds nascent RNA polymerase III transcripts, stabilizing these RNAs against exonucleases. Here we report that the La protein also functions in the assembly of certain RNA polymerase II-transcribed RNAs into RNPs. A mutation in a core protein of the spliceosomal snRNPs, Smd1p, causes yeast cells to require the La protein Lhp1p for growth at low temperatures. Precursors to U1, U2, U4 and U5 RNAs are bound by Lhp1p in both wild-type and mutant cells. At the permissive temperature, smd1-1 cells contain higher levels of stable U1 and U5 snRNPs when Lhp1p is present. At low temperatures, Lhp1p becomes essential for the accumulation of U4/U6 snRNPs and for cell viability. When U4 RNA is added to extracts, the pre-U4 RNA, but not the mature RNA, is bound by Smd1p. These results suggest that, by stabilizing a 3'-extended form of U4 RNA, Lhp1p facilitates efficient Sm protein binding, thus assisting formation of the U4/U6 snRNP.
authors.affiliation: Departments of Cell Biology and Molecular Biophysics and Biochemistry, Howard Hughes Medical Institute, Yale University School of Medicine, 295 Congress Avenue, New Haven, CT 06536, USA.
authors.forename: D
authors.initials: D
authors.lastname: Xue
authors.forename: D A
authors.initials: DA
authors.lastname: Rubinson
authors.forename: B K
authors.initials: BK
authors.lastname: Pannone
authors.forename: C J
authors.initials: CJ
authors.lastname: Yoo
authors.forename: S L
authors.initials: SL
authors.lastname: Wolin
mesh_terms: D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D005800:Genes, Fungal; D009154:Mutation; D011485:Protein Binding; D012322:RNA Precursors / Q000235:genetics / Q000378:metabolism; D020871:RNA Stability; D012331:RNA, Fungal / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D017412:Ribonucleoprotein, U1 Small Nuclear / Q000235:genetics / Q000378:metabolism; D017414:Ribonucleoprotein, U4-U6 Small Nuclear / Q000235:genetics / Q000378:metabolism; D017411:Ribonucleoproteins, Small Nuclear / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D017381:Spliceosomes / Q000378:metabolism
chemical_list: D017931:DNA Primers; D005656:Fungal Proteins; C088396:LHP1 protein, S cerevisiae; D012322:RNA Precursors; D012331:RNA, Fungal; D016601:RNA-Binding Proteins; D017412:Ribonucleoprotein, U1 Small Nuclear; D017414:Ribonucleoprotein, U4-U6 Small Nuclear; D017411:Ribonucleoproteins, Small Nuclear; D029701:Saccharomyces cerevisiae Proteins