Importin/karyopherin protein family members required for mRNA export from the nucleus.
The yeast Saccharomyces cerevisiae contains three proteins (Kap104p, Pse1p, and Kap123p) that share similarity to the 95-kDa beta subunit of the nuclear transport factor importin (also termed karyopherin and encoded by KAP95/RSL1 in yeast). Proteins that contain nuclear localization sequences are recognized in the cytoplasm and delivered to the nucleus by the heterodimeric importin complex. A second importin-related protein, transportin, delivers a subset of heterogeneous nuclear ribonucleoproteins (hnRNPs) to the nucleoplasm. We now show that in contrast to loss of importin beta (Kap95p/Rsl1p) and transportin (Kap104p), conditional loss of Pse1p in a strain lacking Kap123p results in a specific block of mRNA export from the nucleus. Overexpression of Sxm1p, a protein related to Cse1p in yeast and to the human cellular apoptosis susceptibility protein, relieves the defects of cells lacking Pse1p and Kap123p. Thus, a major role of Pse1p, Kap123p, and Sxm1p may be nuclear export rather than import, suggesting a symmetrical relationship between these processes.
Seedorf
M
M
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School and Dana-Farber Cancer Institute, 44 Binney Street, Boston, MA 02115, USA.
Silver
P A
PA
D001692:Biological Transport; D002467:Cell Nucleus / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D028884:Karyopherins; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D012331:RNA, Fungal / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*
D005656:Fungal Proteins; D028884:Karyopherins; D009687:Nuclear Proteins; D012331:RNA, Fungal; D012333:RNA, Messenger