Rapid targeting of nuclear proteins to the cytoplasm.
BACKGROUND
The transcription factor NF-ATc plays a key role in the activation of many early immune response genes and is regulated by subcellular localization. NF-ATc translocates from the cytoplasm to the nucleus in response to a rise in intracellular calcium, and immediately returns to the cytoplasm when intracellular calcium levels fall. The rapid nuclear exit of NF-ATc is thought to be one mechanism by which cells distinguish between sustained and transient calcium signals.


RESULTS
To study the nuclear export of NF-ATc, we have developed a general, non-invasive assay for the identification and study of nuclear export signals (NESs). The NES is defined by its ability to translocate a protein from the nucleus to the cytoplasm when the two are tethered by a membrane-permeable ligand. This procedure has allowed us to identify a NES within NF-ATc that functions in concert with a glycogen synthase kinase-regulated process to direct the rapid nuclear exit of NF-ATc.


CONCLUSIONS
The rapid nuclear export of NF-ATc via its NES and a glycogen synthase kinase-regulated event may be an important mechanism for insulating cells from transient spikes in intracellular calcium which might otherwise lead to inappropriate activation. The assay we have developed allows the rapid identification of NESs and can be used as a general method for the inducible cytoplasmic export of nuclear proteins.
Klemm
J D
JD
Howard Hughes Medical Institute, Department of Developmental Biology, Stanford University School of Medicine, Stanford, California 94305, USA.
Beals
C R
CR
Crabtree
G R
GR
D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport; D019556:COS Cells; D002118:Calcium / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism*; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D019084:Fluorescent Antibody Technique, Indirect; D008969:Molecular Sequence Data; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins / Q000378:metabolism*; D010957:Plasmids; D021382:Protein Sorting Signals / Q000737:chemistry / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013601:T-Lymphocytes / Q000378:metabolism; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*
D004268:DNA-Binding Proteins; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D004247:DNA; D002118:Calcium