title: All small nuclear RNAs (snRNAs) of the [U4/U6.U5] Tri-snRNP localize to nucleoli; Identification of the nucleolar localization element of U6 snRNA.
abstract: Previously, we showed that spliceosomal U6 small nuclear RNA (snRNA) transiently passes through the nucleolus. Herein, we report that all individual snRNAs of the [U4/U6.U5] tri-snRNP localize to nucleoli, demonstrated by fluorescence microscopy of nucleolar preparations after injection of fluorescein-labeled snRNA into Xenopus oocyte nuclei. Nucleolar localization of U6 is independent from [U4/U6] snRNP formation since sites of direct interaction of U6 snRNA with U4 snRNA are not nucleolar localization elements. Among all regions in U6, the only one required for nucleolar localization is its 3' end, which associates with the La protein and subsequently during maturation of U6 is bound by Lsm proteins. This 3'-nucleolar localization element of U6 is both essential and sufficient for nucleolar localization and also required for localization to Cajal bodies. Conversion of the 3' hydroxyl of U6 snRNA to a 3' phosphate prevents association with the La protein but does not affect U6 localization to nucleoli or Cajal bodies.
authors.affiliation: Division of Biology and Medicine, Brown University, Providence, Rhode Island 02912, USA.
authors.forename: Susan A
authors.initials: SA
authors.lastname: Gerbi
authors.forename: Thilo Sascha
authors.initials: TS
authors.lastname: Lange
mesh_terms: D000818:Animals; D001483:Base Sequence; D002466:Cell Nucleolus / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D020541:Coiled Bodies / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009154:Mutation; D009690:Nucleic Acid Conformation; D009865:Oocytes / Q000378:metabolism; D011233:Precipitin Tests; D012342:RNA, Small Nuclear / Q000378:metabolism*; D017411:Ribonucleoproteins, Small Nuclear / Q000378:metabolism*; D012689:Sequence Homology, Nucleic Acid; D013997:Time Factors; D014981:Xenopus / Q000196:embryology
chemical_list: D012342:RNA, Small Nuclear; D017411:Ribonucleoproteins, Small Nuclear; C405486:U6 small nuclear RNA; D004247:DNA