The karyopherin Msn5/Kap142 requires Nup82 for nuclear export and performs a function distinct from translocation in RPA protein import.
Protein transport between the nucleus and cytoplasm requires interactions between nuclear pore complex proteins (nucleoporins) and soluble nuclear transport factors (karyopherins, importins, and exportins). Exactly how these interactions contribute to the nucleocytoplasmic transport of substrates remains unclear. Using a synthetic lethal screen with the nucleoporin NUP1, we have identified a conditional allele of NUP82, encoding an essential nuclear pore complex protein in Saccharomyces cerevisiae. This nup82-3 allele also exhibits synthetic genetic interactions with mutants of the karyopherin MSN5. nup82-3 mutants accumulate the Msn5 export substrate Pho4 within the nucleus at non-permissive temperatures. The nuclear import of the RPA complex subunit Rfa2 is impaired in nup82-3 and in mutants of the karyopherin KAP95, but is not affected by the loss of MSN5. Interestingly, deletion of MSN5 results in retention of Rfa2-GFP within the nucleus under conditions in which it normally diffuses out. These data provide evidence that Nup82 is important for Msn5-mediated nuclear protein export and Kap95-mediated protein import. In addition, Msn5 may play a role independent of import in the localization of Rfa2.
Belanger
Kenneth D
KD
Department of Biology, Colgate University, Hamilton, New York 13346, USA. kbelanger@mail.colgate.edu
Simmons
Laura A
LA
Roth
Jessica K
JK
VanderPloeg
Kristin A
KA
Lichten
Lauren B
LB
Fahrenkrog
Birthe
B
D021581:Active Transport, Cell Nucleus / Q000502:physiology*; D001483:Base Sequence; D017931:DNA Primers; D017930:Genes, Reporter; D028884:Karyopherins / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D028861:Nuclear Pore Complex Proteins / Q000235:genetics / Q000378:metabolism*; D010957:Plasmids; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic / Q000235:genetics; D021381:Protein Transport / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D013816:Thermodynamics
D017931:DNA Primers; D028884:Karyopherins; C401306:MSN5 protein, S cerevisiae; C095897:NUP82 protein, S cerevisiae; D028861:Nuclear Pore Complex Proteins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins