title: Sam68 is a Ras-GAP-associated protein in mitosis.
abstract: Sam68 is the major tyrosine-phosphorylated and Src-associated protein in mitotic cells. Sam68 stimulates G1/S transition and this effect is dependent on the integrity of its KH domain (hnRNPK Homology) which confers nucleic acid binding properties. During mitosis, Sam68 undergoes tyrosine phosphorylation, which negatively regulates its nucleic acid binding properties and mediates the interaction of Sam68 with critical SH2-containing signaling proteins such as Grb2, PLC gamma 1 and Ras-GAP. However, the interaction of Ras-GAP with Sam68 has been brought into question, based on the lack of co-immunoprecipitation between Sam68 and Ras-GAP in interphase cells. Here we show that the choice of anti-Ras-GAP antibodies is critical for the detection of Ras-GAP/Sam68 complex formation, and that this interaction is specific for G2/M transition in both NIH3T3 and Src-transformed cells. Such data reinforce the importance of the interaction of Ras-GAP with RNA binding proteins during cell proliferation through its SH2 and SH3 domains.
authors.affiliation: Gene Medicine Department, Rhône-Poulenc Rorer, Vitry sur Seine, France.
authors.forename: E
authors.initials: E
authors.lastname: Guitard
authors.forename: I
authors.initials: I
authors.lastname: Barlat
authors.forename: F
authors.initials: F
authors.lastname: Maurier
authors.forename: F
authors.initials: F
authors.lastname: Schweighoffer
authors.forename: B
authors.initials: B
authors.lastname: Tocque
mesh_terms: D016475:3T3 Cells; D000818:Animals; D000906:Antibodies / Q000276:immunology / Q000378:metabolism; D002453:Cell Cycle / Q000502:physiology; D004268:DNA-Binding Proteins / Q000378:metabolism*; D020690:GTPase-Activating Proteins; D016391:Genes, src / Q000235:genetics; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D051379:Mice; D008938:Mitosis / Q000502:physiology*; D008954:Models, Biological; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D011233:Precipitin Tests; D011506:Proteins / Q000276:immunology / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism*; D012261:Ribonucleoproteins / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D014170:Transformation, Genetic / Q000235:genetics; D020703:ras GTPase-Activating Proteins
chemical_list: D000906:Antibodies; D004268:DNA-Binding Proteins; C489561:Dok1 protein, mouse; C074561:GAP-associated protein p62; D020690:GTPase-Activating Proteins; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D010750:Phosphoproteins; D011506:Proteins; D016601:RNA-Binding Proteins; D012261:Ribonucleoproteins; D020703:ras GTPase-Activating Proteins