title: The ubiquitin-conjugating enzyme UbcM2 can regulate the stability and activity of the antioxidant transcription factor Nrf2.
abstract: The transcription factor nuclear factor E2-related factor 2 (Nrf2) induces the expression of antioxidant gene products that neutralize reactive oxygen species and restore redox homeostasis. Nrf2 is constitutively degraded by the ubiquitin proteolytic system in unperturbed cells, but this turnover is arrested in response to oxidative stress, thereby leading to Nrf2 accumulation. Yet, a mechanistic understanding of how Nrf2 stabilization and transcriptional activation are coupled remains to be determined. We have discovered that the ubiquitin-conjugating enzyme UbcM2 is a novel regulator of Nrf2. Recombinant Nrf2 and UbcM2 form a complex upon alkylation of a non-catalytic cysteine in UbcM2, Cys-136. Substitution of this cysteine with a phenylalanine (C136F) to mimic cysteine oxidation/alkylation results in constitutive binding of UbcM2 to Nrf2 and an increased half-life of the transcription factor in vivo. We provide evidence that UbcM2 and Nrf2 form a nuclear complex utilizing the DNA binding, Neh1 domain, of Nrf2. Finally, we demonstrate that UbcM2 can enhance the transcriptional activity of endogenous Nrf2 and that Cys-136 and the active-site cysteine, Cys-145, jointly contribute to this regulation. Collectively, these data identify UbcM2 as a novel component of the Nrf2 regulatory circuit and position cysteine 136 as a putative redox sensor in this signaling pathway. This work implicates UbcM2 in the restoration of redox homeostasis following oxidative stress.
authors.affiliation: Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA.
authors.forename: Kendra S
authors.initials: KS
authors.lastname: Plafker
authors.forename: Linda
authors.initials: L
authors.lastname: Nguyen
authors.forename: Mark
authors.initials: M
authors.lastname: Barneche
authors.forename: Saima
authors.initials: S
authors.lastname: Mirza
authors.forename: David
authors.initials: D
authors.lastname: Crawford
authors.forename: Scott M
authors.initials: SM
authors.lastname: Plafker
mesh_terms: D000595:Amino Acid Sequence; D020134:Catalytic Domain; D003545:Cysteine / Q000378:metabolism; D006367:HeLa Cells; D006706:Homeostasis; D006801:Humans; D008969:Molecular Sequence Data; D051267:NF-E2-Related Factor 2 / Q000737:chemistry* / Q000378:metabolism*; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D015533:Transcriptional Activation; D025801:Ubiquitin / Q000378:metabolism; D044763:Ubiquitin-Conjugating Enzymes / Q000737:chemistry / Q000378:metabolism*
chemical_list: D051267:NF-E2-Related Factor 2; D025801:Ubiquitin; D044763:Ubiquitin-Conjugating Enzymes; D003545:Cysteine