title: SUN-1 and ZYG-12, mediators of centrosome-nucleus attachment, are a functional SUN/KASH pair in Caenorhabditis elegans.
abstract: Klarsicht/ANC-1/Syne/homology (KASH)/Sad-1/UNC-84 (SUN) protein pairs can act as connectors between cytoplasmic organelles and the nucleoskeleton. Caenorhabditis elegans ZYG-12 and SUN-1 are essential for centrosome-nucleus attachment. Although SUN-1 has a canonical SUN domain, ZYG-12 has a divergent KASH domain. Here, we establish that the ZYG-12 mini KASH domain is functional and, in combination with a portion of coiled-coil domain, is sufficient for nuclear envelope localization. ZYG-12 and SUN-1 are hypothesized to be outer and inner nuclear membrane proteins, respectively, and to interact, but neither their topologies nor their physical interaction has been directly investigated. We show that ZYG-12 is a type II outer nuclear membrane (ONM) protein and that SUN-1 is a type II inner nuclear membrane protein. The proteins interact in the luminal space of the nuclear envelope via the ZYG-12 mini KASH domain and a region of SUN-1 that does not include the SUN domain. SUN-1 is hypothesized to restrict ZYG-12 to the ONM, preventing diffusion through the endoplasmic reticulum. We establish that ZYG-12 is indeed immobile at the ONM by using fluorescence recovery after photobleaching and show that SUN-1 is sufficient to localize ZYG-12 in cells. This work supports current models of KASH/SUN pairs and highlights the diversity in sequence elements defining KASH domains.
authors.affiliation: Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA. iminn1@jhmi.edu
authors.forename: I L
authors.initials: IL
authors.lastname: Minn
authors.forename: Melissa M
authors.initials: MM
authors.lastname: Rolls
authors.forename: Wendy
authors.initials: W
authors.lastname: Hanna-Rose
authors.forename: Christian J
authors.initials: CJ
authors.lastname: Malone
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism*; D018385:Centrosome / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D009685:Nuclear Envelope / Q000378:metabolism; D017434:Protein Structure, Tertiary; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020798:Two-Hybrid System Techniques
chemical_list: D029742:Caenorhabditis elegans Proteins; D018797:Cell Cycle Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D011993:Recombinant Fusion Proteins; C514114:sun-1 protein, C elegans; C480800:zyg-12 protein, C elegans