title: Mammalian U6 small nuclear RNA undergoes 3' end modifications within the spliceosome.
abstract: Mammalian U6 small nuclear RNA (snRNA) is heterogeneous with respect to the number of 3' terminal U residues. The major form terminates with five U residues and a 2',3' cyclic phosphate. Because of the presence in HeLa cell nuclear extracts of a terminal uridylyl transferase, a minor form of U6 snRNA is elongated, producing multiple species containing up to 12 U residues. In this study we have used glycerol gradients to demonstrate that these U6 snRNA forms are assembled into U6 ribonucleoprotein (RNP), U4/U6 snRNPs, and U4/U5/U6 tri-snRNP complexes. Furthermore, glycerol gradients combined with affinity selection of biotinylated pre-mRNAs led us to show that elongated forms of U6 snRNAs enter the spliceosome and that some of these become shortened with time to a single species having the same characteristics as the major form of U6 snRNA present in mammalian nuclear extracts. We propose that this elongation-shortening process is related to the function of U6 snRNA in mammalian pre-mRNA splicing.
authors.affiliation: Laboratoire de Biochimie, CRLC Val d'Aurelle-Paul Lamarque, Parc Euromédecine, Montpellier, France.
authors.forename: J
authors.initials: J
authors.lastname: Tazi
authors.forename: T
authors.initials: T
authors.lastname: Forne
authors.forename: P
authors.initials: P
authors.lastname: Jeanteur
authors.forename: G
authors.initials: G
authors.lastname: Cathala
authors.forename: C
authors.initials: C
authors.lastname: Brunel
mesh_terms: D001482:Base Composition; D002467:Cell Nucleus / Q000378:metabolism; D002474:Cell-Free System; D014644:Genetic Variation; D006367:HeLa Cells; D006801:Humans; D046911:Macromolecular Substances; D009690:Nucleic Acid Conformation; D012322:RNA Precursors / Q000378:metabolism; D012326:RNA Splicing; D012342:RNA, Small Nuclear / Q000302:isolation & purification / Q000378:metabolism*; D017414:Ribonucleoprotein, U4-U6 Small Nuclear / Q000378:metabolism; D017381:Spliceosomes / Q000378:metabolism*; D014158:Transcription, Genetic; D006599:UDPglucose-Hexose-1-Phosphate Uridylyltransferase / Q000378:metabolism; D014542:Uridine Monophosphate / Q000378:metabolism*
chemical_list: D046911:Macromolecular Substances; D012322:RNA Precursors; D012342:RNA, Small Nuclear; D017414:Ribonucleoprotein, U4-U6 Small Nuclear; D014542:Uridine Monophosphate; D006599:UDPglucose-Hexose-1-Phosphate Uridylyltransferase