title: Down-regulation of c-Fos/c-Jun AP-1 dimer activity by sumoylation.
abstract: The inducible transcriptional complex AP-1, composed of c-Fos and c-Jun proteins, is crucial for cell adaptation to many environmental changes. While its mechanisms of activation have been extensively studied, how its activity is restrained is poorly understood. We report here that lysine 265 of c-Fos is conjugated by the peptidic posttranslational modifiers SUMO-1, SUMO-2, and SUMO-3 and that c-Jun can be sumoylated on lysine 257 as well as on the previously described lysine 229. Sumoylation of c-Fos preferentially occurs in the context of c-Jun/c-Fos heterodimers. Using nonsumoylatable mutants of c-Fos and c-Jun as well as a chimeric protein mimicking sumoylated c-Fos, we show that sumoylation entails lower AP-1 transactivation activity. Interestingly, single sumoylation at any of the three acceptor sites of the c-Fos/c-Jun dimer is sufficient to substantially reduce transcription activation. The lower activity of sumoylated c-Fos is not due to inhibition of protein entry into the nucleus, accelerated turnover, and intrinsic inability to dimerize or to bind to DNA. Instead, cell fractionation experiments suggest that decreased transcriptional activity of sumoylated c-Fos is associated with specific intranuclear distribution. Interestingly, the phosphorylation of threonine 232 observed upon expression of oncogenically activated Ha-Ras is known to superactivate c-Fos transcriptional activity. We show here that it also inhibits c-Fos sumoylation, revealing a functional antagonism between two posttranslational modifications, each occurring within a different moiety of a bipartite transactivation domain of c-Fos. Finally we report that the sumoylation of c-Fos is a dynamic process that can be reversed via multiple mechanisms. This supports the idea that this modification does not constitute a final inactivation step that necessarily precedes protein degradation.
authors.affiliation: Institute of Molecular Genetics of Montpellier, UMR5535/IFR122, CNRS 1919, France.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Bossis
authors.forename: Cécile E
authors.initials: CE
authors.lastname: Malnou
authors.forename: Rosa
authors.initials: R
authors.lastname: Farras
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Andermarcher
authors.forename: Robert
authors.initials: R
authors.lastname: Hipskind
authors.forename: Manuel
authors.initials: M
authors.lastname: Rodriguez
authors.forename: Darja
authors.initials: D
authors.lastname: Schmidt
authors.forename: Stefan
authors.initials: S
authors.lastname: Muller
authors.forename: Isabelle
authors.initials: I
authors.lastname: Jariel-Encontre
authors.forename: Marc
authors.initials: M
authors.lastname: Piechaczyk
mesh_terms: D001665:Binding Sites; D019281:Dimerization; D015536:Down-Regulation; D015972:Gene Expression Regulation, Neoplastic; D005982:Glutathione Transferase / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D007700:Kinetics; D008156:Luciferases / Q000378:metabolism; D008239:Lysine / Q000737:chemistry; D008856:Microscopy, Fluorescence; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism*; D016755:Proto-Oncogene Proteins c-jun / Q000737:chemistry / Q000378:metabolism*; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D025842:SUMO-1 Protein / Q000378:metabolism; D025841:Small Ubiquitin-Related Modifier Proteins / Q000378:metabolism; D013347:Subcellular Fractions; D013912:Threonine / Q000737:chemistry; D013997:Time Factors; D018808:Transcription Factor AP-1 / Q000737:chemistry / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection
chemical_list: D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D011993:Recombinant Fusion Proteins; D025842:SUMO-1 Protein; C117909:SUMO2 protein, human; D025841:Small Ubiquitin-Related Modifier Proteins; D018808:Transcription Factor AP-1; D013912:Threonine; D008156:Luciferases; D005982:Glutathione Transferase; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras); D008239:Lysine