Journal
CELLULAR PHYSIOLOGY AND BIOCHEMISTRY
Volume 46, Issue 1, Pages 418-430Publisher
KARGER
DOI: 10.1159/000488475
Keywords
Nrf2; Nuclear degradation; Sumoylation; Promyelocytic leukemia-nuclear bodies; RNF111/Arkadia; K48-linked ubiquitination
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Funding
- NIH [SC1CA143985, 2 S21MD000104, 5 R25GM0599994]
- CTSA from the National Center for Advancing Translational Sciences [ULITR000445]
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Background/Aims: The transcription factor Nrf2 is a master regulator of the antioxidant defense system, protecting cells from oxidative damage. We previously reported that the SUMO-targeted E3 ubiquitin ligase (STUbL), RING finger protein 4 (RNF4) accelerated the degradation rate of Nrf2 in promyelocytic leukemia-nuclear body (PML-NB)-enriched fractions and decreased Nrf2-mediated gene transcription. The mechanisms that regulate Nrf2 nuclear levels are poorly understood. In this study, we aim to explore the role of the second mammalian STUbL, Arkadia/RNF111 on Nrf2. Methods: Arkadia mediated ubiquitination was detected using co-immunoprecipitation assays in which whole cell lysates were immunoprecipated with anti-Nrf2 antibody and Western blotted with anti-hemagglutinin (HA) antibody or anti-Lys-48 ubiquitin-specific antibody. The half-life of Nrf2 was detected in whole cell lysates and promyelocytic leukemia-nuclear body enriched fractions by cycloheximide-chase. Reporter gene assays were performed using the antioxidant response element (ARE)-containing promoter Heme oxygenase-1 (HO-1). Results: We show that Arkadia/RNF111 is able to ubiquitinate Nrf2 resulting in the stabilization of Nrf2. This stabilization was mediated through Lys-48 ubiquitin chains, contrary to traditionally degradative role of Lys-48 ubiquitination, suggesting that Lys-48 ubiquitination of Nrf2 protects Nrf2 from degradation thereby allowing Nrf2-dependent gene transcription. Conclusion: Collectively, these findings highlight a novel mechanism to positively regulate nuclear Nrf2 levels in response to oxidative stress through Arkadia-mediated K48-linked ubiquitination of Nrf2. (C) 2018 The Author(s) Published by S. Karger AG, Basel
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