title: Distinct roles for DH and PH domains in the Lbc oncogene.
abstract: Members of the Dbl-homology (DH) family of proteins promote guanine nucleotide exchange on Rho GTPases. Lbc, which specifically acts on Rho but not Rac or Cdc42, was isolated as a transforming oncogene and is composed of a DH and a Pleckstrin-homology (PH) domain. We show here that the Lbc DH domain alone is capable of stimulating new DNA synthesis in quiescent fibroblasts and Rho-dependent actin stress fiber assembly. However, the PH domain is required for subcellular localization of Lbc along actin stress fibers and for efficient transformation of NIH3T3 cells. The results show that, in contrast to other Dbl-homology proteins, the PH domain of Lbc is dispensable for activation of Rho in vivo. The PH domain-dependent subcellular localization of Lbc may, however, be important for growth factor activation of endogenous Lbc and for oncogenic transformation.
authors.affiliation: Department of Biochemistry, University College London, UK.
authors.forename: M F
authors.initials: MF
authors.lastname: Olson
authors.forename: P
authors.initials: P
authors.lastname: Sterpetti
authors.forename: K
authors.initials: K
authors.lastname: Nagata
authors.forename: D
authors.initials: D
authors.lastname: Toksoz
authors.forename: A
authors.initials: A
authors.lastname: Hall
mesh_terms: D016475:3T3 Cells; D054758:A Kinase Anchor Proteins; D000199:Actins / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001792:Blood Platelets / Q000502:physiology; D001798:Blood Proteins / Q000235:genetics / Q000502:physiology*; D002471:Cell Transformation, Neoplastic / Q000235:genetics; D004261:DNA Replication / Q000235:genetics; D020662:Guanine Nucleotide Exchange Factors; D007399:Interphase / Q000235:genetics; D051379:Mice; D015778:Minor Histocompatibility Antigens; D010750:Phosphoproteins; D017434:Protein Structure, Tertiary; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000502:physiology; D011506:Proteins / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000502:physiology*; D011519:Proto-Oncogenes; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: D054758:A Kinase Anchor Proteins; C085467:AKAP13 protein, human; D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D001798:Blood Proteins; D020662:Guanine Nucleotide Exchange Factors; C512843:Mcf2 protein, mouse; D015778:Minor Histocompatibility Antigens; D010750:Phosphoproteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; C039077:platelet protein P47; D011505:Protein-Tyrosine Kinases