In vivo evidence for involvement of a 58 kDa component of nuclear pore-targeting complex in nuclear protein import.
We recently showed that a nuclear location signal (NLS)-containing karyophile forms a stable complex with cytoplasmic components for nuclear pore-targeting The complex, termed nuclear pore-targeting complex (PTAC), contained two essential proteins of 54 and 90 kDa, respectively, as estimated by electrophoresis. In this study, we found that the 54 kDa component of PTAC is the mouse homologue of Xenopus importin (m-importin). Cytoplasmic injection of the antibodies raised against recombinant m-importin showed an inhibitory effect on nuclear import of a karyophile in living mammalian cells. A portion of cytoplasmically injected antibodies migrated rapidly into the nucleus, indicating dynamic movement of this protein across the nuclear envelope. Moreover, the injected antibodies co-precipitated the karyophile, in an NLS-dependent manner, with endogenous m-importin in the cytoplasm. These results provide in vivo evidence that m-importin is involved in nuclear protein import through association with a NLS in the cytoplasm before nuclear pore binding.
Imamoto
N
N
Department of Anatomy and Cell Biology, Osaka University Medical School, Japan.
Shimamoto
T
T
Takao
T
T
Tachibana
T
T
Kose
S
S
Matsubae
M
M
Sekimoto
T
T
Shimonishi
Y
Y
Yoneda
Y
Y
D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies / Q000378:metabolism; D001483:Base Sequence; D001693:Biological Transport, Active; D002352:Carrier Proteins / Q000235:genetics; D002460:Cell Line; D003593:Cytoplasm / Q000378:metabolism; D006801:Humans; D028884:Karyopherins; D051379:Mice; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009685:Nuclear Envelope / Q000378:metabolism*; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D017386:Sequence Homology, Amino Acid; D028901:alpha Karyopherins; D028961:beta Karyopherins
D000906:Antibodies; D002352:Carrier Proteins; C490630:KPNA2 protein, human; D028884:Karyopherins; C490631:Kpna2 protein, mouse; C094999:Kpnb1 protein, mouse; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; D011993:Recombinant Fusion Proteins; D028901:alpha Karyopherins; D028961:beta Karyopherins; C087978:karyopherin alpha 2