title: Nuclear accumulation of the U1 snRNP-specific protein C is due to diffusion and retention in the nucleus.
abstract: The U1 small nuclear ribonucleoprotein particle (snRNP) has an important function in the early formation of the spliceosome, the multicomponent complex in which pre-mRNA splicing takes place. The nuclear localization signals of two of the three U1 snRNP-specific proteins, U1-70K and U1A, have been mapped. Both proteins are transported actively to the nucleus. Here we show by microinjection of Xenopus laevis oocytes that the third U1 snRNP-specific protein, U1C, passively enters the nucleus. Furthermore, we show that in both X. laevis oocytes and cultured HeLa cells mutant U1C proteins that are not able to bind to the U1 snRNP do not accumulate in the nucleus, indicating that nuclear accumulation of U1C is due to incorporation of the protein into the U1 snRNP.
authors.affiliation: Department of Biochemistry, University of Nijmegen, Nijmegen, 6500 HB, The Netherlands.
authors.forename: J M
authors.initials: JM
authors.lastname: Klein Gunnewiek
authors.forename: Y
authors.initials: Y
authors.lastname: van Aarssen
authors.forename: A
authors.initials: A
authors.lastname: van der Kemp
authors.forename: R
authors.initials: R
authors.lastname: Nelissen
authors.forename: G J
authors.initials: GJ
authors.lastname: Pruijn
authors.forename: W J
authors.initials: WJ
authors.lastname: van Venrooij
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism*; D004058:Diffusion; D005260:Female; D006367:HeLa Cells; D006801:Humans; D008845:Microinjections; D009865:Oocytes / Q000502:physiology; D014176:Protein Biosynthesis; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017412:Ribonucleoprotein, U1 Small Nuclear / Q000378:metabolism*; D013762:Tetrahydrofolate Dehydrogenase / Q000096:biosynthesis / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection; D014982:Xenopus laevis
chemical_list: D011993:Recombinant Fusion Proteins; D017412:Ribonucleoprotein, U1 Small Nuclear; D013762:Tetrahydrofolate Dehydrogenase