title: MEKK1 regulates the AP-1 dimer repertoire via control of JunB transcription and Fra-2 protein stability.
abstract: Activator protein 1 (AP-1) transcription factor dimers are composed of Jun, Fos, and ATF member proteins, but the mechanisms that determine AP-1 composition are not clearly defined and the function of specific dimers is not well understood. MEKK1 is a mitogen-activated protein kinase (MAPK) kinase kinase and an ubiquitin ligase that regulates both the extracellular signal-regulated kinase 1/2 and the c-Jun amino-terminal kinase. Herein, we demonstrate that MEKK1 regulates the AP-1 protein repertoire. Both FGF-2 and phorbol ester-inducible urokinase-type plasminogen activator (uPA) expression requires AP-1 binding to an enhancer element in the uPA promoter, and we have previously shown that FGF-2 or PMA induction of uPA expression is strongly dependent on MEKK1. JunB mRNA is significantly increased in MEKK1-/- cells, demonstrating that MEKK1 suppresses JunB mRNA expression. Upregulation of JunB expression in MEKK1-/- cells forms an inhibitory AP-1 complex that binds to the uPA promoter and inhibits uPA transcription. MEKK1 also regulates Fra-2 protein stability by inducing Fra-2 ubiquitination and degradation. MEKK1 regulates AP-1-dependent gene expression by regulating the expression, activity and degradation of component members of the AP-1 complex. Controlling the repertoire of a transcription factor complex is a newly defined function for an MAPK kinase kinase.
authors.affiliation: Department of Pharmacology, Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, NC 27599-7365, USA. bruce_cuevas@med.unc.edu
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Cuevas
authors.forename: Mark T
authors.initials: MT
authors.lastname: Uhlik
authors.forename: Timothy P
authors.initials: TP
authors.lastname: Garrington
authors.forename: Gary L
authors.initials: GL
authors.lastname: Johnson
mesh_terms: D000818:Animals; D001483:Base Sequence; D002467:Cell Nucleus / Q000502:physiology; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism*; D019281:Dimerization; D004622:Embryo, Mammalian; D005347:Fibroblasts; D051921:Fos-Related Antigen-2; D048728:MAP Kinase Kinase Kinase 1 / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D051379:Mice; D008969:Molecular Sequence Data; D015345:Oligonucleotide Probes; D011401:Promoter Regions, Genetic; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D014568:Urokinase-Type Plasminogen Activator / Q000235:genetics
chemical_list: D004268:DNA-Binding Proteins; D051921:Fos-Related Antigen-2; C497873:Fosl2 protein, mouse; D015345:Oligonucleotide Probes; D016755:Proto-Oncogene Proteins c-jun; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D048728:MAP Kinase Kinase Kinase 1; D014568:Urokinase-Type Plasminogen Activator; D013755:Tetradecanoylphorbol Acetate