TitleCap-independent Nrf2 translation is part of a lipoic acid-stimulated detoxification stress response.
Publication TypeJournal Article
Year of Publication2012
AuthorsShay KPetersen, Michels AJ, Li W, Kong A-NTony, Hagen TM
JournalBiochim Biophys Acta
Date Published2012 Jun
KeywordsBase Sequence, Cell Compartmentation, Cell Nucleus, Hep G2 Cells, Humans, Inactivation, Metabolic, NF-E2-Related Factor 2, Proteasome Endopeptidase Complex, Proteasome Inhibitors, Protein Biosynthesis, RNA Caps, Sirolimus, Stress, Physiological, Thioctic Acid

Little is known about either the basal or stimulated homeostatic mechanisms regulating nuclear tenure of Nf-e2-related factor 2 (Nrf2), a transcription factor that mediates expression of over 200 detoxification genes. Our data show that stress-induced nuclear Nrf2 accumulation is largely from de novo protein synthesis, rather than translocation from a pre-existing cytoplasmic pool. HepG2 cells were used to monitor nuclear Nrf2 24h following treatment with the dithiol micronutrient (R)-α-lipoic acid (LA; 50μM), or vehicle. LA caused a ≥2.5-fold increase in nuclear Nrf2 within 1h. However, pretreating cells with cycloheximide (50μg/ml) inhibited LA-induced Nrf2 nuclear accumulation by 94%. Providing cells with the mTOR inhibitor, rapamycin, decreased basal Nrf2 levels by 84% after 4h, but LA overcame this inhibition. LA-mediated de novo protein translation was confirmed using HepG2 cells transfected with a bicistronic construct containing an internal ribosome entry sequence (IRES) for Nrf2, with significant (P<0.05) increase in IRES use under LA treatment. These results suggest that a dithiol stimulus mediates Nrf2 nuclear tenure via cap-independent protein translation. Thus, translational control of Nrf2 synthesis, rather than reliance solely on pre-existing protein, may mediate the rapid burst of Nrf2 nuclear accumulation following stress stimuli.

Alternate JournalBiochim. Biophys. Acta
PubMed ID22521877
PubMed Central IDPMC4012555
Grant ListR01 AG017141 / AG / NIA NIH HHS / United States
T32 AT002688-01 / AT / NCCIH NIH HHS / United States
R01 2AG17141 / AG / NIA NIH HHS / United States
P30 ES005022 / ES / NIEHS NIH HHS / United States
T32 AT002688 / AT / NCCIH NIH HHS / United States
P01 AT002034 / AT / NCCIH NIH HHS / United States
P01 AT002034-01 / AT / NCCIH NIH HHS / United States