title: Stimulation of gene induction and cell growth by the Ras effector Rlf.
abstract: Rlf is a ubiquitously expressed distinct relative of RalGDS that interacts with active Ras in vitro. We now demonstrate that Rlf, when co-expressed with Ras mutants, associates in vivo with RasV12 and the effector-domain mutant RasV12G37, but not with RasV12E38 or RasV12C40. Rlf exhibits guanine nucleotide exchange activity towards the small GTPase Ral and, importantly, Rlf-induced Ral activation is stimulated by active Ras. In addition, RasV12 and RasV12G37 synergize with Rlf in the transcriptional activation of the c-fos promoter. Rlf, when targeted to the plasma membrane using the Ras farnesyl attachment site (Rlf-CAAX), is constitutively active, inducing both Ral activation and c-fos promoter activity. Rlf-CAAX-induced gene expression is insensitive to dominant negative Ras and the MEK inhibitor PD98059, and involves activation of the serum response element. Furthermore, expression of Rlf-CAAX is sufficient to induce proliferation of NIH 3T3 cells under low-serum conditions. These data demonstrate that Rlf is an effector of Ras which functions as an exchange factor for Ral. Rlf mediates a distinct Ras-induced signalling pathway to gene induction. Finally, a constitutively active form of Rlf can stimulate transcriptional activation and cell growth.
authors.affiliation: Laboratory for Physiological Chemistry, Utrecht University, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands.
authors.forename: R M
authors.initials: RM
authors.lastname: Wolthuis
authors.forename: N D
authors.initials: ND
authors.lastname: de Ruiter
authors.forename: R H
authors.initials: RH
authors.lastname: Cool
authors.forename: J L
authors.initials: JL
authors.lastname: Bos
mesh_terms: D016475:3T3 Cells; D000818:Animals; D019556:COS Cells; D002451:Cell Compartmentation; D002455:Cell Division; D002462:Cell Membrane; D002471:Cell Transformation, Neoplastic; D019204:GTP-Binding Proteins / Q000378:metabolism; D005786:Gene Expression Regulation; D020662:Guanine Nucleotide Exchange Factors; D006150:Guanine Nucleotides / Q000378:metabolism; D048369:MAP Kinase Kinase 1; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases; D017368:Protein Prenylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis*; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation; D020725:ral GTP-Binding Proteins; D020663:ras Guanine Nucleotide Exchange Factors; D018631:ras Proteins / Q000378:metabolism*
chemical_list: D020662:Guanine Nucleotide Exchange Factors; D006150:Guanine Nucleotides; D011506:Proteins; D016760:Proto-Oncogene Proteins c-fos; C490805:Rgl2 protein, mouse; D014157:Transcription Factors; D020663:ras Guanine Nucleotide Exchange Factors; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; D048369:MAP Kinase Kinase 1; C482125:MAP2K1 protein, human; C482127:Map2k1 protein, mouse; D020929:Mitogen-Activated Protein Kinase Kinases; D019204:GTP-Binding Proteins; D020725:ral GTP-Binding Proteins; D018631:ras Proteins