Coordinated Sumoylation and Ubiquitination Modulate EGF Induced EGR1 Expression and Stability

Abstract

BackgroundHuman 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.MethodsWe 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.ResultsWe 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.ConclusionsHere we demonstrate that SUMO-1 modification improving EGR1 ubiquitination is involved in the modulation of its stability upon EGF mediated induction.

The Biarylpyrazole Compound AM251 Alters Mitochondrial Physiology via Proteolytic Degradation of ERRα

“…In the current study, AM251 significantly increased SUMOylation of ERRa by SUMO-2,3 (Fig. 4B), a posttranslational modification associated with enhanced protein turnover (Miteva et al, 2010;Manente et al, 2011;Shimshon et al, 2011). Consistent with these findings, protein modifications with SUMO-2,3 have been associated with increased nuclear degradation (Anderson et al, 2012).…”

“…Previous mutagenesis studies have identified the critical importance of residues Lys-14 and Lys-403 for ERRa SUMOylation (Vu et al, 2007;Tremblay et al, 2008) and found this modification to also occur in vivo (Tremblay et al, 2008). SUMOylation has previously been linked to either the promotion (Manente et al, 2011) or inhibition (Anderson et al, 2012;Sharma et al, 2010) of protein ubiquitination. Despite ERRa being a target of ubiquitination by the E3 ligase Parkin (Ren et al, 2011), our preliminary findings failed to show any significant induction of ERRa ubiquitination by AM251 (data not shown).…”

Egr‐1: new conductor for the tissue repair orchestra directs harmony (regeneration) or cacophony (fibrosis)

“…One prominent pathway for Egr-1 modification is acetylation, which generally leads to diminished Egr-1 activity by negative feedback loops [25]. On the other hand, Egr-1 activity is positively regulated by its phosphorylation [25,26] and sumoylation [27,28]. The nature of post-translational modifications targeting the Egr-1 protein influences both the choice of its target genes as well as its transcriptional activity.…”

Egr-1 Maintains NSC Proliferation and Its Overexpression Counteracts Cell Cycle Exit Triggered by the Withdrawal of Epidermal Growth Factor

“…Previous studies on Egr-1 showed that both its DNA-binding ability and transcriptional activities may be influenced by posttranslational modifications [41,42]. In Western blots of aNSC extracts, upon EGF treatment, we detected a doublet of 84 and 82 kDa, the phosphorylated and unphosphorylated forms of Egr-1, respectively [43].…”