title: Nucleoporins NPP-10, NPP-13 and NPP-20 are required for HCP-4 nuclear import to establish correct centromere assembly.
abstract: Centromeres form a chromosomal platform for the assembly of the kinetochores, which are required for orderly chromosome segregation. Assembly of both centromeres and kinetochores proceeds by a step-by-step mechanism that is regulated in time and space. It has been suggested that the regulated nuclear import of centromeric proteins is involved in this process. We show that the knockdown of nucleoporins NPP-10, NPP-13 and NPP-20 inCaenorhabditiselegansaffects early steps in centromere formation and sister centromere resolution, and results in severe chromosomal defects in the early embryo. These phenotypes mirror the knockdown phenotype of HCP-4 (an ortholog of mammalian CENP-C), a key factor for centromere formation and inner kinetochore assembly. HCP-4 is present in the cytoplasm during interphase. It is imported into nuclei and assembled in centromeres during prophase. Following the knockdown of NPP-10, NPP-13 and NPP-20, HCP-4 remains in the cytosol throughout prophase due to stalled import. In prometaphase and later mitotic stages after breakdown of the nuclear envelope, HCP-4 is not incorporated into centromeres. These results indicate that correct timing of the availability of HCP-4 by nuclear import is essential.
authors.affiliation: Cytogenetics group, Institute of Biology, Humboldt-Universität zu Berlin, Chausseestr. 117, Berlin 10115, Germany jorgeferreira27@gmail.com.
authors.forename: Jorge
authors.identifier: 0000-0002-1972-0353
authors.initials: J
authors.lastname: Ferreira
authors.affiliation: University of New South Wales, School of Medical Sciences, Sydney, New South Wales 2052, Australia.
authors.forename: Jeffrey H
authors.initials: JH
authors.lastname: Stear
authors.affiliation: Cytogenetics group, Institute of Biology, Humboldt-Universität zu Berlin, Chausseestr. 117, Berlin 10115, Germany jorgeferreira27@gmail.com.
authors.forename: Harald
authors.initials: H
authors.lastname: Saumweber
mesh_terms: D021581:Active Transport, Cell Nucleus; D000818:Animals; D017173:Caenorhabditis elegans / Q000166:cytology / Q000196:embryology / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism*; D002503:Centromere / Q000378:metabolism*; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000378:metabolism; D055785:Gene Knockdown Techniques; D008677:Metaphase; D008938:Mitosis; D008954:Models, Biological; D009685:Nuclear Envelope / Q000378:metabolism; D028861:Nuclear Pore Complex Proteins / Q000378:metabolism*; D011418:Prophase; D034622:RNA Interference
chemical_list: D029742:Caenorhabditis elegans Proteins; D028861:Nuclear Pore Complex Proteins
keywords: C. elegans embryo; Centromere; Mitosis; Nucleoporins