title: The SUN protein UNC-84 is required only in force-bearing cells to maintain nuclear envelope architecture.
abstract: The nuclear envelope (NE) consists of two evenly spaced bilayers, the inner and outer nuclear membranes. The Sad1p and UNC-84 (SUN) proteins and Klarsicht, ANC-1, and Syne homology (KASH) proteins that interact to form LINC (linker of nucleoskeleton and cytoskeleton) complexes connecting the nucleoskeleton to the cytoskeleton have been implicated in maintaining NE spacing. Surprisingly, the NE morphology of most Caenorhabditis elegans nuclei was normal in the absence of functional SUN proteins. Distortions of the perinuclear space observed in unc-84 mutant muscle nuclei resembled those previously observed in HeLa cells, suggesting that SUN proteins are required to maintain NE architecture in cells under high mechanical strain. The UNC-84 protein with large deletions in its luminal domain was able to form functional NE bridges but had no observable effect on NE architecture. Therefore, SUN-KASH bridges are only required to maintain NE spacing in cells subjected to increased mechanical forces. Furthermore, SUN proteins do not dictate the width of the NE.
authors.affiliation: Department of Molecular and Cellular Biology and Department of Physics, University of California, Davis, Davis, CA 95616.
authors.forename: Natalie E
authors.initials: NE
authors.lastname: Cain
authors.affiliation: Department of Molecular and Cellular Biology and Department of Physics, University of California, Davis, Davis, CA 95616.
authors.forename: Erin C
authors.initials: EC
authors.lastname: Tapley
authors.affiliation: Electron Microscope Laboratory, University of California, Berkeley, Berkeley, CA 94720.
authors.forename: Kent L
authors.initials: KL
authors.lastname: McDonald
authors.affiliation: Department of Molecular and Cellular Biology and Department of Physics, University of California, Davis, Davis, CA 95616.
authors.forename: Benjamin M
authors.initials: BM
authors.lastname: Cain
authors.affiliation: Department of Molecular and Cellular Biology and Department of Physics, University of California, Davis, Davis, CA 95616 dastarr@ucdavis.edu.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Starr
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D009685:Nuclear Envelope / Q000378:metabolism* / Q000648:ultrastructure; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D010812:Physical Stimulation; D013312:Stress, Physiological
chemical_list: D029742:Caenorhabditis elegans Proteins; D008562:Membrane Glycoproteins; D009687:Nuclear Proteins; C120560:Unc-84 protein, C elegans