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© The Rockefeller University Press,
0021-9525/2000//1027 $5.00
The Journal of Cell Biology, Volume 149, Number 5,
, 2000 1027-1038
Original Article |
Yeast Nucleoporins Involved in Passive Nuclear Envelope Permeability
dasg{at}mail.rochester.edu
The vertebrate nuclear pore complex (NPC) harbors an
10-nm diameter diffusion channel that is large enough to admit 50-kD polypeptides. We have analyzed the permeability properties of the Saccharomyces cerevisiae nuclear envelope (NE) using import (NLS) and export (NES) signal-containing green fluorescent protein (GFP) reporters. Compared with wild-type, passive export rates of a classical karyopherin/importin (Kap) Kap60p/Kap95p-targeted NLS-GFP reporter (cNLS-GFP) were significantly faster in nup188-
and nup170-
cells. Similar results were obtained using two other NLS-GFP reporters, containing either the Kap104p-targeted Nab2p NLS (rgNLS) or the Kap121p-targeted Pho4p NLS (pNLS). Elevated levels of Hsp70 stimulated cNLS-GFP import, but had no effect on the import of rgNLS-GFP. Thus, the role of Hsp70 in NLS-directed import may be NLS- or targeting pathway-specific. Equilibrium sieving limits for the diffusion channel were assessed in vivo using NES-GFP reporters of 36–126 kD and were found to be greater than wild-type in nup188-
and nup170-
cells. We propose that Nup170p and Nup188p are involved in establishing the functional resting diameter of the NPC's central transport channel.
Key Words: nuclear pore complex import/export signals green fluorescent protein diffusion channel Saccharomyces cerevisiae
© 2000 The Rockefeller University Press
Abbreviations used in this paper: cNLS-GFP, classical Kap60p/Kap95p-targeted NLS-GFP reporter; Ea, Arrhenius energy of activation; FG, phenylalanine–glycine repeats; GFP, green fluorescent protein; Kap, karyopherin/importin β family of Arm/HEAT repeat-containing factors; NE, nuclear envelope; NES, nuclear export signal; NLS, nuclear import signal; NPC, nuclear pore complex; nups, nucleoporins; pNLS, Kap121p-targeted Pho4p NLS; rgNLS, Kap104p-targeted Nab2p NLS; wt, wild-type.
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