title: Regulation and composition of activator protein 1 (AP-1) transcription factors controlling collagenase and c-Jun promoter activities.
abstract: The activator protein 1 (AP-1) transcription factor is composed of heterodimers of the Fos/activating transcription factor (ATF) and Jun subfamilies of basic-region leucine-zipper (B-ZIP) proteins. In order to determine the identities of individual B-ZIP proteins in various AP-1 complexes we tested the effect of dominant-negative mutants to the B-ZIP proteins c-Fos, ATF2, ATF4 and CCAAT-enhancer-binding protein (C/EBP) on the activities of the collagenase and c-Jun promoters. These dominant-negative mutants inhibit DNA binding of wild-type B-ZIP proteins in a leucine-zipper-dependent fashion. Transcription of a collagenase promoter/reporter gene was induced in HepG2 hepatoma cells by expression of c-Fos and c-Jun, administration of PMA ("TPA") or by expression of a truncated form of MEK (mitogen-activated/extracellular-signal-regulated kinase kinase) kinase-1, MEKK1Delta. In all cases, the dominant-negative mutants A-Fos and A-ATF2 decreased collagenase promoter activity. However, A-ATF4 and A-C/EBP had no effect. A-Fos and A-ATF2 also reduced MEKK1Delta-induced stimulation of the c-Jun promoter. In contrast, constitutive c-Jun promoter activity was blocked solely by A-ATF2, strongly suggesting that ATF2 and/or an ATF2-dimerizing protein are of major importance for c-Jun transcription in unstimulated cells. These results demonstrate that AP-1 transcription factors of different compositions control c-jun gene transcription in resting or stimulated cells.
authors.affiliation: Department of Medical Biochemistry and Molecular Biology, Building 44, University of Saarland, D-66421 Homburg, Germany.
authors.forename: L
authors.initials: L
authors.lastname: Steinmüller
authors.forename: G
authors.initials: G
authors.lastname: Cibelli
authors.forename: J R
authors.initials: JR
authors.lastname: Moll
authors.forename: C
authors.initials: C
authors.lastname: Vinson
authors.forename: G
authors.initials: G
authors.lastname: Thiel
mesh_terms: D000595:Amino Acid Sequence; D006528:Carcinoma, Hepatocellular; D002478:Cells, Cultured; D017364:Collagenases / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic; D017930:Genes, Reporter; D016758:Genes, jun; D006801:Humans; D016350:Leucine Zippers; D008113:Liver Neoplasms; D048728:MAP Kinase Kinase Kinase 1; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011401:Promoter Regions, Genetic; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D018808:Transcription Factor AP-1 / Q000737:chemistry / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D016755:Proto-Oncogene Proteins c-jun; D011994:Recombinant Proteins; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D017346:Protein Serine-Threonine Kinases; D048728:MAP Kinase Kinase Kinase 1; C482576:MAP3K1 protein, human; D017364:Collagenases