Disease relevance of NSP1

• To investigate the molecular basis underlying complex formation, recombinant full-length Nup49p and Nup57p and the carboxyl-terminal domain of Nsp1p, which lacks the FXFG repeat domain, were expressed in Escherichia coli [1].

High impact information on NSP1

• An essential yeast protein, Nup145p, is identified via its genetic interaction with the nucleoporin Nsp1p [2].
• The 85 kd subunit (p85 alpha) lacks Pl3-kinase activity and acts as an adaptor, coupling the 110 kd subunit (p110) to activated protein tyrosine kinases [3].
• The central domain of NUP1 consists of a series of degenerate repeats similar to those found in the nucleoskeletal protein NSP1, a protein that cross-reacts with monoclonal antibodies against NUP1 [4].
• Employing immunoelectron microscopy on yeast cells, we show that NSP1 is located at the nuclear pores [5].
• NSP1: a yeast nuclear envelope protein localized at the nuclear pores exerts its essential function by its carboxy-terminal domain [5].

Biological context of NSP1

• The Nsp1p carboxy-terminal domain is organized into functionally distinct coiled-coil regions required for assembly of nucleoporin subcomplexes and nucleocytoplasmic transport [6].
• NSP1 is located at the nuclear periphery in yeast and is essential for cell growth [5].
• The molecular analysis of the NSP1 protein points to a two domain model: a nonessential domain (the first 603 amino acids) composed of repetitive sequences common to other nuclear proteins and an essential, carboxy-terminal domain (residues 604-823) mediating the vital function of NSP1 [5].
• To further analyze the structural and functional similarity between NSP1 and mammalian nucleoporins, we cloned and sequenced nucleoporin p62 from a HeLa cDNA library [7].
• This result suggests that NSP1 is required for the coordinated cell cycle in S. cerevisiae [8].

Anatomical context of NSP1

• The essential C-terminal domain of NSP1 mediates assembly into the nuclear pore complex (NPC) [9].
• Like NUP1 and NSP1, NUP2 localizes to discrete spots in the nuclear envelope, as determined by indirect immunofluorescence [10].
• Immunoprecipitation from subcellular fractions yields only p110 and p95 from purified nuclei, whereas the approximately 55-kD protein is immunoprecipitated from the soluble fraction [11].
• N-ethylmaleimide treatment of the cytosol as well as antibodies to the nuclear pore protein Nsp1 inhibit import but not binding to the nuclear envelope [12].
• The catalytic subunit of the p85/p110 PI 3'-kinase is homologous to VPS-34, a phosphatidylinositol-specific lipid kinase involved in the sorting of newly synthesized hydrolases to the yeast vacuole [13].

Associations of NSP1 with chemical compounds

• Separate binding sites on nuclear transport factor 2 (NTF2) for GDP-Ran and the phenylalanine-rich repeat regions of nucleoporins p62 and Nsp1p [14].
• Although the p85(IS) domain conferred a strong interaction with the p110 catalytic subunit, this region was not sufficient to impart phosphotyrosine peptide stimulation of PI 3-kinase activity [15].
• Characterization of the PI 3-kinase activity of Vps34p demonstrates that it, unlike the mammalian p110 PI 3-kinase, is highly resistant to the PI 3-kinase inhibitors wortmannin and LY294002 [16].
• Expression of histidine-tagged p33 in yeast in combination with Ni2+ affinity chromatography allows the isolation of a complex containing the p135, p110, p90, p39, and p33 subunits of eIF3 [17].
• Cholesterol sulfate and sulfatide inhibit the free catalytic subunit p110 alpha but fail to inhibit the homologous phosphatidylinositol 3-kinase from Saccharomyces cerevisiae (Vps34p), suggesting that these sulfated lipids act specifically on the mammalian phosphatidylinositol 3-kinase [18].

Physical interactions of NSP1

• Nic96p has been isolated previously in a complex together with the nuclear pore proteins Nsp1p, Nup49p and a p54 polypeptide [19].
• A novel nuclear pore protein Nup82p which specifically binds to a fraction of Nsp1p [20].
• In this study, we demonstrate that Nup159p specifically interacts through this domain with both Nsp1p and Nup82p [21].
• Here we report that the yeast protein Gsp1p can directly bind to the nucleoporin Nsp1p in vitro [22].

Regulatory relationships of NSP1

• The essential yeast nuclear pore protein NSP1 was placed under the control of the regulatable GAL10 promoter [23].

Other interactions of NSP1

• Conversely, affinity purification of tagged NSP49 enriches for NSP1, the p54 and the NIC96 component [9].
• Accordingly, interaction of Nup82p with Nsp1p coil 2 is competed by excess Nup57p [6].
• Strains mutant for Nup133p or Nsp1p accumulated lower levels of several unspliced pre-tRNAs [24].
• The Nup82 protein can be divided into at least two different domains both required for the essential function, but it is only the carboxy-terminal domain, exhibiting heptad repeats, which binds to Nsp1p [20].
• Decreased levels of NPC-associated Nsp1p and Nup116p were observed [25].

Analytical, diagnostic and therapeutic context of NSP1

• To identify components which interact physically with this yeast nucleoporin, the tagged C-terminal domain of NSP1 (ProtA-NSP1) was isolated by affinity chromatography under non-denaturing conditions [9].
• Examination of subcellular fractions by immunoblotting shows that both p110 and p95 are located exclusively in the nuclear fraction [11].
• Digestion of purified nuclei with DNase to produce nuclear envelopes releases some of p110, but the majority of p110 is solubilized only after treatment of envelopes with 1 M NaCl [11].

References