title: The Mediator Subunit MED16 Transduces NRF2-Activating Signals into Antioxidant Gene Expression.
abstract: The KEAP1-NRF2 system plays a central role in cytoprotection. NRF2 is stabilized in response to electrophiles and activates transcription of antioxidant genes. Although robust induction of NRF2 target genes confers resistance to oxidative insults, how NRF2 triggers transcriptional activation after binding to DNA has not been elucidated. To decipher the molecular mechanisms underlying NRF2-dependent transcriptional activation, we purified the NRF2 nuclear protein complex and identified the Mediator subunits as NRF2 cofactors. Among them, MED16 directly associated with NRF2. Disruption of Med16 significantly attenuated the electrophile-induced expression of NRF2 target genes but did not affect hypoxia-induced gene expression, suggesting a specific requirement for MED16 in NRF2-dependent transcription. Importantly, we found that 75% of NRF2-activated genes exhibited blunted inductions by electrophiles in Med16-deficient cells compared to wild-type cells, which strongly argues that MED16 is a major contributor supporting NRF2-dependent transcriptional activation. NRF2-dependent phosphorylation of the RNA polymerase II C-terminal domain was absent in Med16-deficient cells, suggesting that MED16 serves as a conduit to transmit NRF2-activating signals to RNA polymerase II. MED16 indeed turned out to be essential for cytoprotection against oxidative insults. Thus, the KEAP1-NRF2-MED16 axis has emerged as a new regulatory pathway mediating the antioxidant response through the robust activation of NRF2 target genes.
authors.affiliation: Department of Medical Biochemistry, Tohoku University Graduate School of Medicine, Sendai, Japan Department of Gene Expression Regulation, Institute of Development, Aging and Cancer, Tohoku University, Sendai, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Sekine
authors.affiliation: Department of Gene Expression Regulation, Institute of Development, Aging and Cancer, Tohoku University, Sendai, Japan.
authors.forename: Keito
authors.initials: K
authors.lastname: Okazaki
authors.affiliation: Department of Gene Expression Regulation, Institute of Development, Aging and Cancer, Tohoku University, Sendai, Japan.
authors.forename: Nao
authors.initials: N
authors.lastname: Ota
authors.affiliation: Department of Biochemistry, Tohoku University Graduate School of Medicine, Sendai, Japan CREST, AMED, Sendai, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Shima
authors.affiliation: Tohoku Medical Megabank Organization, Tohoku University, Sendai, Japan.
authors.forename: Yasutake
authors.initials: Y
authors.lastname: Katoh
authors.affiliation: Division of Interdisciplinary Medical Science, Tohoku University Graduate School of Medicine, Sendai, Japan.
authors.forename: Norio
authors.initials: N
authors.lastname: Suzuki
authors.affiliation: Department of Biochemistry, Tohoku University Graduate School of Medicine, Sendai, Japan.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Igarashi
authors.affiliation: Laboratory of Hematology, Division of Medical Biophysics, Kobe University Graduate School of Health Sciences, Kobe, Japan.
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Ito
authors.affiliation: Department of Gene Expression Regulation, Institute of Development, Aging and Cancer, Tohoku University, Sendai, Japan hozumim@med.tohoku.ac.jp masiyamamoto@med.tohoku.ac.jp.
authors.forename: Hozumi
authors.initials: H
authors.lastname: Motohashi
authors.affiliation: Department of Medical Biochemistry, Tohoku University Graduate School of Medicine, Sendai, Japan Tohoku Medical Megabank Organization, Tohoku University, Sendai, Japan hozumim@med.tohoku.ac.jp masiyamamoto@med.tohoku.ac.jp.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Yamamoto
mesh_terms: D000818:Animals; D002460:Cell Line; D049109:Cell Proliferation; D005786:Gene Expression Regulation; D055786:Gene Knockout Techniques; D006801:Humans; D008099:Liver / Q000378:metabolism; D056892:Mediator Complex / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism*; D018384:Oxidative Stress; D010766:Phosphorylation; D054730:Protein Interaction Domains and Motifs; D060066:Protein Interaction Maps; D012319:RNA Polymerase II / Q000378:metabolism; D015398:Signal Transduction
chemical_list: C000608113:MED16 protein, mouse; D056892:Mediator Complex; D051267:NF-E2-Related Factor 2; C495636:Nfe2l2 protein, mouse; D012319:RNA Polymerase II