title: Differential phosphorylation and subcellular localization of La RNPs associated with precursor tRNAs and translation-related mRNAs.
abstract: The La protein facilitates the production of tRNAs in the nucleus and the translation of specific mRNAs in the cytoplasm. We report that human La that is phosphorylated on serine 366 (pLa) is nucleoplasmic and associated with precursor tRNAs and other nascent RNA polymerase III transcripts while nonphosphorylated (np)La is cytoplasmic and associated with a subset of mRNAs that contain 5'-terminal oligopyrimidine (5'TOP) motifs known to control protein synthesis. Thus, La ribonucleoproteins (RNP) exist in distinct states that differ in subcellular localization, serine 366 phosphorylation, and associated RNAs. These results are consistent with a model in which the relative concentrations of the La S366 isoforms in different subcellular compartments in conjunction with the relative concentrations of specific RNA ligands in these compartments determine the differential association of npLa and pLa with their respective classes of associated RNAs.
authors.affiliation: Laboratory of Molecular Growth Regulation, National Institute of Child Health and Development, Bethesda, MD 20892, USA.
authors.forename: Robert V
authors.initials: RV
authors.lastname: Intine
authors.forename: Scott A
authors.initials: SA
authors.lastname: Tenenbaum
authors.forename: Amy L
authors.initials: AL
authors.lastname: Sakulich
authors.forename: Jack D
authors.initials: JD
authors.lastname: Keene
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Maraia
mesh_terms: D045163:Antibodies, Phospho-Specific / Q000378:metabolism; D001324:Autoantigens; D006367:HeLa Cells; D006801:Humans; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D014176:Protein Biosynthesis; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012320:RNA Polymerase III / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D012343:RNA, Transfer / Q000235:genetics / Q000378:metabolism*; D012261:Ribonucleoproteins / Q000235:genetics / Q000378:metabolism*; D012694:Serine / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D000097585:SS-B Antigen
chemical_list: D045163:Antibodies, Phospho-Specific; D001324:Autoantigens; D009687:Nuclear Proteins; D020033:Protein Isoforms; D012320:RNA Polymerase III; D012333:RNA, Messenger; D012343:RNA, Transfer; D012261:Ribonucleoproteins; D012694:Serine; D000097585:SS-B Antigen