title: A pre-export U1 snRNP in Xenopus laevis oocyte nuclei.
abstract: We demonstrate that precursors of U1 snRNA are associated with nuclear proteins prior to export to the cytoplasm. The approximately 15S complexes containing pre-U1 RNA, which we call pre-export U1 snRNPs, were identified in extracts of Xenopus laevis oocyte nuclei that were synthesizing U1 RNAs from injected U1 genes. The U1 snRNP-specific A protein was associated with nuclear pre-U1 RNA since both this protein and the RNA were co-precipitated by antibodies directed against either the m7G-cap of the precursor RNA or the U1-A protein. The interaction of the U1-A protein with pre-U1 RNA required sequences in the loop II region although this region of U1 RNA was not necessary for the association of U1 A protein with mature U1 snRNPs. The U1 A protein helps protect pre-U1 RNA against degradation in the nucleus.
authors.affiliation: Department of Biomolecular Chemistry, University of Wisconsin, Madison 53706.
authors.forename: M P
authors.initials: MP
authors.lastname: Terns
authors.forename: E
authors.initials: E
authors.lastname: Lund
authors.forename: J E
authors.initials: JE
authors.lastname: Dahlberg
mesh_terms: D000818:Animals; D001692:Biological Transport; D002451:Cell Compartmentation; D002467:Cell Nucleus / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism*; D012323:RNA Processing, Post-Transcriptional; D017412:Ribonucleoprotein, U1 Small Nuclear / Q000737:chemistry / Q000378:metabolism*; D014982:Xenopus laevis
chemical_list: D009687:Nuclear Proteins; D017412:Ribonucleoprotein, U1 Small Nuclear