title: Human ninein is a centrosomal autoantigen recognized by CREST patient sera and plays a regulatory role in microtubule nucleation.
abstract: Centrosome is the major microtubule organizing center in mammalian cells that plays a critical role in a variety of cellular events by the microtubule arrays emanating from it. Despite its significance, the molecular mechanisms underlying the structure and function of the centrosome are still not clear. Herein we describe the identification of three isotypes of human ninein by expression library screening with autoimmune sera from CREST patients. All three ninein isotypes exhibit centrosomal localization throughout the cell cycle when GFP-tagged fusion proteins are expressed transiently in mammalian cells. Construction of serial deletions of GFP-tagged ninein reveals that a stretch of three leucine zippers with a flanking sequence is required and sufficient for centrosomal targeting. Overexpression of ninein results in mislocalization of gamma-tubulin, recruiting it to ectopic (noncentrosomal) ninein-containing sites which are not active in nucleating microtubules. In these cells, nucleation of microtubules from the centrosome is also inhibited. These results thus suggest a regulatory role for ninein in microtubule nucleation.
authors.affiliation: Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
authors.forename: Elizabeth E
authors.initials: EE
authors.lastname: Stillwell
authors.forename: Jun
authors.initials: J
authors.lastname: Zhou
authors.forename: Harish C
authors.initials: HC
authors.lastname: Joshi
mesh_terms: D000818:Animals; D001323:Autoantibodies / Q000097:blood / Q000276:immunology; D001324:Autoantigens / Q000097:blood / Q000737:chemistry / Q000276:immunology*; D017675:CREST Syndrome / Q000097:blood / Q000276:immunology* / Q000503:physiopathology; D018385:Centrosome / Q000276:immunology* / Q000378:metabolism; D003598:Cytoskeletal Proteins; D019204:GTP-Binding Proteins / Q000097:blood / Q000737:chemistry / Q000276:immunology*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D016350:Leucine Zippers / Q000502:physiology; D051379:Mice; D022101:Microtubule-Organizing Center / Q000276:immunology* / Q000378:metabolism; D008870:Microtubules / Q000276:immunology* / Q000378:metabolism; D008938:Mitosis / Q000502:physiology; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D020033:Protein Isoforms / Q000276:immunology / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D008941:Spindle Apparatus / Q000276:immunology / Q000378:metabolism; D014404:Tubulin / Q000378:metabolism
chemical_list: D001323:Autoantibodies; D001324:Autoantigens; D003598:Cytoskeletal Proteins; C512806:NIN protein, human; C099035:Nin protein, mouse; D009687:Nuclear Proteins; D020033:Protein Isoforms; D014404:Tubulin; D049452:Green Fluorescent Proteins; D019204:GTP-Binding Proteins