title: Sm protein down-regulation leads to defects in nuclear pore complex disassembly and distribution in C. elegans embryos.
abstract: Nuclear pore complexes (NPCs) are large macromolecular structures embedded in the nuclear envelope (NE), where they facilitate exchange of molecules between the cytoplasm and the nucleoplasm. In most cell types, NPCs are evenly distributed around the NE. However, the mechanisms dictating NPC distribution are largely unknown. Here, we used the model organism Caenorhabditis elegans to identify genes that affect NPC distribution during early embryonic divisions. We found that down-regulation of the Sm proteins, which are core components of the spliceosome, but not down-regulation of other splicing factors, led to clustering of NPCs. Down-regulation of Sm proteins also led to incomplete disassembly of NPCs during mitosis, but had no effect on lamina disassembly, suggesting that the defect in NPC disassembly was not due to a general defect in nuclear envelope breakdown. We further found that these mitotic NPC remnants persisted on an ER membrane that juxtaposes the mitotic spindle. At the end of mitosis, the remnant NPCs moved toward the chromatin and the reforming NE, where they ultimately clustered by forming membrane stacks perforated by NPCs. Our results suggest a novel, splicing-independent, role for Sm proteins in NPC disassembly, and point to a possible link between NPC disassembly in mitosis and NPC distribution in the subsequent interphase.
authors.affiliation: The Laboratory of Molecular and Cellular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, 8 Center Drive, Bethesda MD 20892, USA.
authors.forename: Daphna
authors.initials: D
authors.lastname: Joseph-Strauss
authors.forename: Mátyás
authors.initials: M
authors.lastname: Gorjánácz
authors.forename: Rachel
authors.initials: R
authors.lastname: Santarella-Mellwig
authors.forename: Ekaterina
authors.initials: E
authors.lastname: Voronina
authors.forename: Anjon
authors.initials: A
authors.lastname: Audhya
authors.forename: Orna
authors.initials: O
authors.lastname: Cohen-Fix
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000196:embryology* / Q000235:genetics / Q000648:ultrastructure; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism; D015536:Down-Regulation; D004625:Embryo, Nonmammalian; D008938:Mitosis; D022022:Nuclear Pore / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D034622:RNA Interference; D017411:Ribonucleoproteins, Small Nuclear / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D017381:Spliceosomes / Q000235:genetics / Q000378:metabolism
chemical_list: D029742:Caenorhabditis elegans Proteins; D017411:Ribonucleoproteins, Small Nuclear; C573504:SNR-1 protein, C elegans