The import pathway of human and Thermoplasma 20S proteasomes into HeLa cell nuclei is different from that of classical NLS-bearing proteins.
Wild-type proteasomes of human erythrocytes and the archaeon Thermoplasma acidophilum compete with each other for transport into nuclei of digitonin-permeabilized HeLa cells in the presence of an energy-regenerating system and rabbit reticulocyte lysate. 'NLS'-mutated Thermoplasma proteasomes were also able to compete with human proteasomes in the same assay, although with lower efficiency. Furthermore, in contrast to the other archaeal and bacterial cell lysates tested, the Thermoplasma cytosol efficiently supported nuclear import of human and Thermoplasma proteasomes. However, the same lysate could barely direct the nuclear transport of BSA-NLSsv40 peptide conjugates or the classical NLS-bearing protein, nucleoplasmin. Finally, additional importin alpha/beta significantly decreased the import efficiency of both human and Thermoplasma proteasomes. Taken together, these results suggest that nuclear import of proteasomes may use a novel pathway that is different from that of classical NLS-bearing proteins.
Mayr
J
J
Max Planck-Institut für Biochemie, Martinsried, Germany.
Wang
H R
HR
Nederlof
P
P
Baumeister
W
W
D000818:Animals; D002463:Cell Membrane Permeability; D002467:Cell Nucleus / Q000378:metabolism*; D003001:Cloning, Molecular; D003546:Cysteine Endopeptidases / Q000235:genetics* / Q000378:metabolism*; D004912:Erythrocytes / Q000201:enzymology; D006367:HeLa Cells; D006801:Humans; D009097:Multienzyme Complexes / Q000235:genetics* / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism; D056489:Nucleoplasmins; D010750:Phosphoproteins / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex; D011817:Rabbits; D011994:Recombinant Proteins / Q000378:metabolism; D012156:Reticulocytes / Q000378:metabolism; D013822:Thermoplasma / Q000201:enzymology*
D009097:Multienzyme Complexes; D009687:Nuclear Proteins; D056489:Nucleoplasmins; D010750:Phosphoproteins; D011994:Recombinant Proteins; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex