The Nsp1p carboxy-terminal domain is organized into functionally distinct coiled-coil regions required for assembly of nucleoporin subcomplexes and nucleocytoplasmic transport.
Nucleoporin Nsp1p, which has four predicted coiled-coil regions (coils 1 to 4) in the essential carboxy-terminal domain, is unique in that it is part of two distinct nuclear pore complex (NPC) subcomplexes, Nsp1p-Nup57p-Nup49p-Nic96p and Nsp1p-Nup82p-Nup159p. As shown by in vitro reconstitution, coiled-coil region 2 (residues 673 to 738) is sufficient to form heterotrimeric core complexes and can bind either Nup57p or Nup82p. Accordingly, interaction of Nup82p with Nsp1p coil 2 is competed by excess Nup57p. Strikingly, coil 3 and 4 mutants are still assembled into the core Nsp1p-Nup57p-Nup49p complex but no longer associate with Nic96p. Consistently, the Nsp1p-Nup57p-Nup49p core complex dissociates from the nuclear pores in nsp1 coil 3 and 4 mutant cells, and as a consequence, defects in nuclear protein import are observed. Finally, the nsp1-L640S temperature-sensitive mutation, which maps in coil 1, leads to a strong nuclear mRNA export defect. Thus, distinct coiled-coil regions within Nsp1p-C have separate functions that are related to the assembly of different NPC subcomplexes, nucleocytoplasmic transport, and incorporation into the nuclear pores.
Bailer
S M
SM
Biochemie-Zentrum Heidelberg, D-69120 Heidelberg, Germany. dr.susanne.bailer@med-rz.uni-saarland.de
Balduf
C
C
Hurt
E
E
D021581:Active Transport, Cell Nucleus / Q000502:physiology; D020816:Amino Acid Motifs / Q000502:physiology; D002135:Calcium-Binding Proteins; D002467:Cell Nucleus / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism*; D005656:Fungal Proteins / Q000737:chemistry* / Q000378:metabolism*; D046911:Macromolecular Substances; D008565:Membrane Proteins; D016297:Mutagenesis, Site-Directed; D022022:Nuclear Pore / Q000378:metabolism; D028861:Nuclear Pore Complex Proteins / Q000096:biosynthesis* / Q000378:metabolism; D009687:Nuclear Proteins / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary / Q000502:physiology; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D013329:Structure-Activity Relationship
C116844:ASM4 protein, S cerevisiae; D002135:Calcium-Binding Proteins; D005656:Fungal Proteins; D046911:Macromolecular Substances; D008565:Membrane Proteins; C082533:NIC96 protein, S cerevisiae; C062748:NSP1 protein, S cerevisiae; C077727:NUP49 protein, S cerevisiae; C091559:NUP57 protein, S cerevisiae; C095897:NUP82 protein, S cerevisiae; D028861:Nuclear Pore Complex Proteins; D009687:Nuclear Proteins; D029701:Saccharomyces cerevisiae Proteins