title: Coordinated sumoylation and ubiquitination modulate EGF induced EGR1 expression and stability.
abstract: BACKGROUND
  Human early growth response-1 (EGR1) is a member of the zing-finger family of transcription factors induced by a range of molecular and environmental stimuli including epidermal growth factor (EGF). In a recently published paper we demonstrated that integrin/EGFR cross-talk was required for Egr1 expression through activation of the Erk1/2 and PI3K/Akt/Forkhead pathways. EGR1 activity and stability can be influenced by many different post-translational modifications such as acetylation, phosphorylation, ubiquitination and the recently discovered sumoylation. The aim of this work was to assess the influence of sumoylation on EGF induced Egr1 expression and/or stability.
  
  
  METHODS
  We modulated the expression of proteins involved in the sumoylation process in ECV304 cells by transient transfection and evaluated Egr1 expression in response to EGF treatment at mRNA and protein levels.
  
  
  RESULTS
  We demonstrated that in ECV304 cells Egr1 was transiently induced upon EGF treatment and a fraction of the endogenous protein was sumoylated. Moreover, SUMO-1/Ubc9 over-expression stabilized EGF induced ERK1/2 phosphorylation and increased Egr1 gene transcription. Conversely, in SUMO-1/Ubc9 transfected cells, EGR1 protein levels were strongly reduced. Data obtained from protein expression and ubiquitination analysis, in the presence of the proteasome inhibitor MG132, suggested that upon EGF stimuli EGR1 sumoylation enhanced its turnover, increasing ubiquitination and proteasome mediated degradation.
  
  
  CONCLUSIONS
  Here we demonstrate that SUMO-1 modification improving EGR1 ubiquitination is involved in the modulation of its stability upon EGF mediated induction.
authors: Dipartimento di Scienze Chimiche, Alimentari, Farmaceutiche e Farmacologiche, University of Piemonte Orientale "A. Avogadro", Novara, Italy.
authors: Arcangela Gabriella
authors: AG
authors: Manente
authors: Giulia
authors: G
authors: Pinton
authors: Daniela
authors: D
authors: Tavian
authors: Gerardo
authors: G
authors: Lopez-Rodas
authors: Elisa
authors: E
authors: Brunelli
authors: Laura
authors: L
authors: Moro
mesh_terms: D002460:Cell Line; D051766:Early Growth Response Protein 1 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D055550:Protein Stability / Q000187:drug effects; D059748:Proteolysis / Q000187:drug effects; D025842:SUMO-1 Protein / Q000378:metabolism; D058207:Sumoylation / Q000187:drug effects*; D013997:Time Factors; D014158:Transcription, Genetic / Q000187:drug effects; D044763:Ubiquitin-Conjugating Enzymes / Q000378:metabolism; D000098843:Ubiquitin-Conjugating Enzyme UBC9
chemical_list: C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; D025842:SUMO-1 Protein; D004815:Epidermal Growth Factor; D044763:Ubiquitin-Conjugating Enzymes; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D046988:Proteasome Endopeptidase Complex; D000098843:Ubiquitin-Conjugating Enzyme UBC9