title: Reversible regulation of the transformed phenotype of ornithine decarboxylase- and ras-overexpressing cells by dominant-negative mutants of c-Jun.
abstract: c-Jun is an oncogenic transcription factor involved in the regulation of cell proliferation, apoptosis and transformation. We have previously reported that cell transformations induced by ornithine decarboxylase (ODC) and c-Ha-ras oncogene, commonly activated in various cancer cells, are associated with constitutively increased phosphorylation of c-Jun on Ser residues 63 and 73. In the present study, we examined the significance of c-Jun phosphorylation and activation on the phenotype of the ODC- and ras-transformants, by using specific inhibitors and dominant-negative (DN) mutants to c-Jun NH(2)-terminal kinase (JNK) and its upstream kinase, SEK1/MKK4 (mitogen-activated protein kinase kinase 4), and to c-Jun. The transformed morphology of both the ODC- and ras-expressing cells was reversed partially by JNK inhibitors and DN JNK1, more effectively by DN SEK1/MKK4 and phosphorylation-deficient c-Jun mutants (c-Jun(S63,73A), c-Jun(S63,73A,T91,93A)) and most potently by a transactivation domain deletion mutant of c-Jun (TAM67). Moreover, tetracycline-inducible TAM67 expression in ODC- and ras-transformed cells showed that the transformed phenotype of the cells is reversibly regulatable. TAM67 also inhibited the tumorigenicity of the cells in nude mice. These inducible cell lines, together with their parental cell lines, provide good models to identify the genes and proteins relevant to cellular transformation.
authors.affiliation: Haartman Institute and Helsinki University Central Hospital, Department of Pathology, University of Helsinki, Helsinki, Finland.
authors.forename: Mari
authors.initials: M
authors.lastname: Kielosto
authors.forename: Pirjo
authors.initials: P
authors.lastname: Nummela
authors.forename: Riikka
authors.initials: R
authors.lastname: Katainen
authors.forename: Virna
authors.initials: V
authors.lastname: Leaner
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Birrer
authors.forename: Erkki
authors.initials: E
authors.lastname: Hölttä
mesh_terms: D000818:Animals; D002471:Cell Transformation, Neoplastic / Q000235:genetics* / Q000378:metabolism; D004318:Doxycycline / Q000494:pharmacology; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D051379:Mice; D008819:Mice, Nude; D020929:Mitogen-Activated Protein Kinase Kinases / Q000235:genetics / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000235:genetics; D009154:Mutation; D041681:NIH 3T3 Cells; D009955:Ornithine Decarboxylase / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D010446:Peptide Fragments / Q000096:biosynthesis / Q000235:genetics; D010766:Phosphorylation; D016755:Proto-Oncogene Proteins c-jun / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D015533:Transcriptional Activation; D014162:Transfection; D018631:ras Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism
chemical_list: D010446:Peptide Fragments; D016755:Proto-Oncogene Proteins c-jun; C439528:TAM67 peptide; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; C482559:MAP2K4 protein, human; C482562:Map2k4 protein, mouse; D020929:Mitogen-Activated Protein Kinase Kinases; D018631:ras Proteins; D009955:Ornithine Decarboxylase; D004318:Doxycycline