The karyopherin Kap95 regulates nuclear pore complex assembly into intact nuclear envelopes in vivo.
Nuclear pore complex (NPC) assembly in interphase cells requires that new NPCs insert into an intact nuclear envelope (NE). Our previous work identified the Ran GTPase as an essential component in this process. We proposed that Ran is required for targeting assembly factors to the cytoplasmic NE face via a novel, vesicular intermediate. Although the molecular target was not identified, Ran is known to function by modulating protein interactions for karyopherin (Kap) beta family members. Here we characterize loss-of-function Saccharomyces cerevisiae mutants in KAP95 with blocks in NPC assembly. Similar to defects in Ran cycle mutants, nuclear pore proteins are no longer localized properly to the NE in kap95 mutants. Also like Ran cycle mutants, the kap95-E126K mutant displayed enhanced lethality with nic96 and nup170 mutants. Thus, Kap95 and Ran are likely functioning at the same stage in assembly. However, although Ran cycle mutants accumulate small cytoplasmic vesicles, cells depleted of Kap95 accumulated long stretches of cytoplasmic membranes and had highly distorted NEs. We conclude that Kap95 serves as a key regulator of NPC assembly into intact NEs. Furthermore, both Kap95 and Ran may provide spatial cues necessary for targeting of vesicular intermediates in de novo NPC assembly.
Ryan
Kathryn J
KJ
Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, TN 37232-8240, USA. kryan@mail.bio.tamu.edu
Zhou
Yingna
Y
Wente
Susan R
SR
D000483:Alleles; D002462:Cell Membrane / Q000648:ultrastructure; D003593:Cytoplasm / Q000378:metabolism; D005820:Genetic Testing; D005973:Glutamine / Q000235:genetics; D008239:Lysine / Q000235:genetics; D008954:Models, Biological; D050505:Mutant Proteins / Q000378:metabolism; D022022:Nuclear Pore / Q000378:metabolism*; D028861:Nuclear Pore Complex Proteins / Q000378:metabolism; D010641:Phenotype; D011485:Protein Binding; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D013696:Temperature; D028961:beta Karyopherins / Q000172:deficiency / Q000378:metabolism*; D020931:ran GTP-Binding Protein / Q000378:metabolism
C000621684:KAP95 protein, S cerevisiae; D050505:Mutant Proteins; D028861:Nuclear Pore Complex Proteins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D028961:beta Karyopherins; D005973:Glutamine; D020931:ran GTP-Binding Protein; D008239:Lysine