title: A novel isoform of sarcolemmal membrane-associated protein (SLMAP) is a component of the microtubule organizing centre.
abstract: The microtubule organizing centre (MTOC) or the centrosome serves a crucial role in the establishment of cellular polarity, organization of interphase microtubules and the formation of the bipolar mitotic spindle. We have elucidated the genomic structure of a gene encoding the sarcolemmal membrane-associated protein (SLMAP), which encodes a 91 kDa polypeptide with a previously uncharacterized N-terminal sequence encompassing a forkhead-associated (FHA) domain that resides at the centrosome. Anti-peptide antibodies directed against SLMAP N-terminal sequences showed colocalization with gamma-tubulin at the centrosomes at all phases of the cell cycle. Agents that specifically disrupt microtubules did not affect SLMAP association with centrosomes. Furthermore, SLMAP sequences directed a reporter green fluorescent protein (GFP) to the centrosome, and deletions of the newly identified N-terminal sequence from SLMAP prevented the centrosomal targeting. Deletion-mutant analysis concluded that overall, structural determinants in SLMAP were responsible for centrosomal targeting. Elevated levels of centrosomal SLMAP were found to be lethal, whereas mutants that lacked centrosomal targeting inhibited cell growth accompanied by an accumulation of cells at the G2/M phase of the cell cycle.
authors.affiliation: Department of Cellular and Molecular Medicine, 451 Smyth Road, University of Ottawa, Ottawa, Ontario, K1H 8M5, Canada.
authors.forename: Rosa M
authors.initials: RM
authors.lastname: Guzzo
authors.forename: Serdal
authors.initials: S
authors.lastname: Sevinc
authors.forename: Maysoon
authors.initials: M
authors.lastname: Salih
authors.forename: Balwant S
authors.initials: BS
authors.lastname: Tuana
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D049109:Cell Proliferation; D018385:Centrosome / Q000737:chemistry* / Q000378:metabolism*; D003001:Cloning, Molecular; D003593:Cytoplasm / Q000378:metabolism; D015698:Genomic Library; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D041681:NIH 3T3 Cells; D009685:Nuclear Envelope / Q000378:metabolism; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport; D014162:Transfection
chemical_list: D008565:Membrane Proteins; D020033:Protein Isoforms; C493783:Slmap protein, mouse