title: Identification of the stef gene that encodes a novel guanine nucleotide exchange factor specific for Rac1.
abstract: The Rho family GTPases are involved in a variety of cellular events by changing the organization of actin cytoskeletal networks in response to extracellular signals. However, it is not clearly known how their activities are spatially and temporally regulated. Here we report the identification of a novel guanine nucleotide exchange factor for Rac1, STEF, which is related in overall amino acid sequence and modular structure to mouse Tiam1 and Drosophila SIF proteins. STEF protein contains two pleckstrin homology domains, a PDZ domain and a Dbl homology domain. The in vitro assay showed that STEF protein specifically enhanced the dissociation of GDP from Rac1 but not that from either RhoA or Cdc42. Expression of a truncated STEF protein in culture cells induced membrane ruffling with altered actin localization, which implies that this protein also activates Rac1 in vivo. The stef transcript was observed in restricted parts of mice, including cartilaginous tissues and the cortical plate of the central nervous system during embryogenesis. These findings suggested that STEF protein participates in the control of cellular events in several developing tissues, possibly changing the actin cytoskeletal network by activating Rac1.
authors.affiliation: Department of Molecular Genetics, National Institute of Neuroscience, NCNP, 4-1-1 Ogawahigashi, Kodaira, Tokyo 187-8502, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Hoshino
authors.forename: M
authors.initials: M
authors.lastname: Sone
authors.forename: M
authors.initials: M
authors.lastname: Fukata
authors.forename: S
authors.initials: S
authors.lastname: Kuroda
authors.forename: K
authors.initials: K
authors.lastname: Kaibuchi
authors.forename: Y
authors.initials: Y
authors.lastname: Nabeshima
authors.forename: C
authors.initials: C
authors.lastname: Hama
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D018797:Cell Cycle Proteins / Q000378:metabolism; D003001:Cloning, Molecular; D016650:Fluorescein-5-isothiocyanate / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D020662:Guanine Nucleotide Exchange Factors; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D007624:KB Cells; D051379:Mice; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D011506:Proteins / Q000737:chemistry / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics; D016415:Sequence Alignment; D014162:Transfection; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae; D020744:rac GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein
chemical_list: D018797:Cell Cycle Proteins; D020662:Guanine Nucleotide Exchange Factors; D011506:Proteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae; D020744:rac GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein; D016650:Fluorescein-5-isothiocyanate