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| TR |
TITLE |
AUTHORS |
KEYWORDS |
MATERIALS & METHODS
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MICROSCOPIC
TECHNIQUES |
SPECIES |
MORPHOLOGY |
CELL
LINE |
| 605 |
Inhibition
of Nuclear Import by the Proapoptotic Protein CC3 |
Frank W. King and
Emma Shtivelman |
cellular protein
CC3/TIP30, nuclear import, transportin, HEAT (huntingtin-elongation A subunit-TOR) |
3T3 cells grown in Dulbecco modified
Eagle medium plus 10% fetal bovine serum on 4-cm glass bottom plates (MatTek Corp.)…
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Fluorescence Microscopy |
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3T3 |
| Abstract |
| |
We report here that the normal cellular protein CC3/TIP30,
when in excess, inhibits nuclear import in vitro and in vivo. CC3 binds directly to the karyopherins
of the importin family in a RanGTP-insensitive manner and associates with nucleoporins in vivo.
CC3 inhibits the nuclear import of proteins possessing either the classical nuclear localization
signal or the M9 signal recognized by transportin. CC3 also inhibits nuclear translocation of
transportin itself. Cells modified to express higher levels of CC3 have a slower rate of nuclear
import and, as described earlier, show an increased sensitivity to death signals. A mutant CC3
protein lacking proapoptotic activity has a lower affinity for transportin, is displaced from
it by RanGTP, and fails to inhibit nuclear import in vitro and in vivo. Together, our results
support a correlation between the ability of CC3 to form a RanGTP-resistant complex with importins,
inhibit nuclear import, and induce apoptosis. Significantly, a dominant-negative form of importin
1 shown previously to inhibit multiple transport pathways induces rapid cell death, strongly
indicating that inhibition of nuclear transport serves as a potent apoptotic signal. |
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