Antibodies against 70-kD heat shock cognate protein inhibit mediated nuclear import of karyophilic proteins.
Previously, we found that anti-DDDED antibodies strongly inhibited in vivo nuclear transport of nuclear proteins and that these antibodies recognized a protein of 69 kD (p69) from rat liver nuclear envelopes that showed specific binding activities to the nuclear location sequences (NLSs) of nucleoplasmin and SV-40 large T-antigen. Here we identified this protein as the 70-kD heat shock cognate protein (hsc70) based on its mass, isoelectric point, cellular localization, and partial amino acid sequences. Competition studies indicated that the recombinant hsc70 expressed in Escherichia coli binds to transport competent SV-40 T-antigen NLS more strongly than to the point mutated transport incompetent mutant NLS. To investigate the possible involvement of hsc70 in nuclear transport, we examined the effect of anti-hsc70 rabbit antibodies on the nuclear accumulation of karyophilic proteins. When injected into the cytoplasm of tissue culture cells, anti-hsc70 strongly inhibited the nuclear import of nucleoplasmin, SV-40 T-antigen NLS bearing BSA and histone H1. In contrast, anti-hsc70 IgG did not prevent the diffusion of lysozyme or 17.4-kD FITC-dextran into the nuclei. After injection of these antibodies, cells continued RNA synthesis and were viable. These results indicate that hsc70 interacts with NLS-containing proteins in the cytoplasm before their nuclear import.
Imamoto
N
N
Institute for Molecular and Cellular Biology, Osaka University, Japan.
Matsuoka
Y
Y
Kurihara
T
T
Kohno
K
K
Miyagi
M
M
Sakiyama
F
F
Okada
Y
Y
Tsunasawa
S
S
Yoneda
Y
Y
D000595:Amino Acid Sequence; D000957:Antigens, Viral, Tumor / Q000378:metabolism; D001667:Binding, Competitive; D001692:Biological Transport; D002352:Carrier Proteins / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism*; D002451:Cell Compartmentation / Q000502:physiology*; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D050883:HSC70 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D006657:Histones / Q000378:metabolism; D006801:Humans; D007526:Isoelectric Point; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009687:Nuclear Proteins / Q000302:isolation & purification / Q000378:metabolism*; D056489:Nucleoplasmins; D010750:Phosphoproteins; D021382:Protein Sorting Signals / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D013539:Simian virus 40 / Q000378:metabolism
D000957:Antigens, Viral, Tumor; D002352:Carrier Proteins; D050883:HSC70 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; C494371:HSPA8 protein, human; D006657:Histones; C494373:Hspa8 protein, rat; D009687:Nuclear Proteins; D056489:Nucleoplasmins; D010750:Phosphoproteins; D021382:Protein Sorting Signals; D011994:Recombinant Proteins