Subcellular distribution and phosphorylation of the nuclear localization signal binding protein, NBP60.
We previously purified a nuclear localization signal binding protein, NBP60, from rat liver (1993, J. Biochem. 113, 308-313). In this study, the subcellular localization of NBP60 was examined using anti-NBP60. Most NBP60 was found to be localized in the nuclear envelope fraction of rat liver obtained on cell fractionation followed by immunoblotting. Staining of the nuclei of cultured cells by the antibody was observed on immunofluorescence microscopy. NBP60 was widely detected in rat nuclear fractions prepared from other tissues and also in nuclei of cultured cells derived from other species. It was shown by immunoelectron microscopy that most NBP60 is present in the nuclear envelope and at least some of that is present on nuclear pore complexes. Although NBP60 was localized in the nuclear envelope in interphase cells, it diffused into the cytoplasm in the mitotic phase. The purified NBP60 was highly phosphorylated by a cdc2 mitotic kinase, whereas nuclear pore proteins p144, p62, p60, and p54 were not phosphorylated by the kinase directly. NBP60 was also phosphorylated by protein kinase A, calmodulin-dependent protein kinase II, and casein kinase II. The phosphorylation of NBP60 by cdc2 kinase and/or the other kinases may be related to the change in the protein's location during the mitotic phase.
Kawahire
S
S
Department of Biochemistry, Faculty of Science, Niigata University, Japan.
Tachibana
T
T
Umemoto
M
M
Yoneda
Y
Y
Imai
N
N
Saito
M
M
Ichimura
T
T
Omata
S
S
Horigome
T
T
D000818:Animals; D000918:Antibody Specificity; D016203:CDC2 Protein Kinase / Q000378:metabolism; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000494:pharmacology; D047390:Casein Kinase II; D002417:Cattle; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology; D002458:Cell Fractionation; D017868:Cyclic AMP-Dependent Protein Kinases / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D005455:Fluorescent Antibody Technique; D006367:HeLa Cells / Q000737:chemistry / Q000201:enzymology / Q000648:ultrastructure; D006801:Humans; D007668:Kidney / Q000166:cytology; D008099:Liver / Q000737:chemistry / Q000201:enzymology; D016253:Microscopy, Immunoelectron; D009685:Nuclear Envelope / Q000737:chemistry / Q000276:immunology / Q000378:metabolism; D009687:Nuclear Proteins / Q000032:analysis* / Q000276:immunology / Q000378:metabolism; D010750:Phosphoproteins / Q000032:analysis* / Q000276:immunology / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013347:Subcellular Fractions / Q000737:chemistry
D004268:DNA-Binding Proteins; C075564:NOLC1 protein, human; C513067:Nolc1 protein, rat; D009687:Nuclear Proteins; D010750:Phosphoproteins; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D016203:CDC2 Protein Kinase