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Up‐regulation of nuclear protein import by nuclear localization signal sequences in living cells
Author(s) -
Tachibana Taro,
Hieda Miki,
Yoneda Yoshihiro
Publication year - 1999
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(98)01664-0
Subject(s) - nls , nuclear localization sequence , nuclear transport , nuclear export signal , cytoplasm , microbiology and biotechnology , nuclear protein , staurosporine , importin , nucleus , phosphorylation , cell nucleus , biology , chemistry , protein kinase a , biochemistry , gene , transcription factor
Using an in vivo assay system, nuclear import ability in individual cells was determined by examining the nuclear import rate. It was found that when a small (not excess) amount of SV40 T‐NLS peptides was co‐injected, the nuclear import rate of SV40 T‐NLS‐containing substrates apparently increased. This up‐regulation was reproduced by the co‐injection of peptides containing bipartite type NLS of CBP80, but not mutated non‐functional NLS peptides, which suggests that these phenomena are specific for functional NLSs. It was further shown that although, in growth‐arrested cells, the nuclear import rate was down‐regulated compared to growing cells, the elevation of the functional import rate by co‐injected NLS peptides reached the same level as in proliferating cells. This up‐regulation was abolished by the addition of a protein kinase inhibitor, staurosporine. These results suggest that although potential nuclear import ability does not vary in each cell, the rate of nuclear import may be controlled by the amount of karyophilic proteins, which need to be carried into the nucleus from the cytoplasm, possibly via an NLS‐dependent phosphorylation reaction.