The role of Nrf1 and Nrf2 in the regulation of copper-responsive transcription.
Recent evidences indicated Nrf2 is more potent than Nrf1 in the activation of antioxidant genes. However, the roles of Nrf proteins in the regulation of copper-responsive transcription have not been well addressed. We took the toxicogenomic approach and the present network and Gene Ontology analyses results showed that Nrf1 and Nrf2 are distinctively involved in copper-responsive transcriptional regulation in HepG2 transcriptome. Cells deficient in either Nrf1 or Nrf2 were more susceptible to copper exposure than wild type cells. Nrf1 and Nrf2 null cells were transfected with the luciferase reporters containing either ARE(s) or a combination of ARE(s) and MREs, and then treated with copper. In Nrf2-null (Nrf2(-/-)) cells, copper did not activate transcription of reporter genes, whereas Nrf1 deficiency did not affect copper-inducible activation. Ectopic expression of Nrf2 restored copper-inducible transcription in Nrf2(-/-) cells. However, the changes in the intrinsic mRNA levels of MT-1 in Nrf null cells following copper treatment showed that Nrf1 and Nrf2 equally contributed to MT-1 activation after 4h, while Nrf1involved more than Nrf2 following 24h exposure. These results suggest that while Nrf2 is crucial for MRE/ARE-mediated transcription in response to copper, Nrf1 may activate MT-1 expression by a mechanism different from that Nrf2 employs.
Department of Biology, College of Natural Sciences, Gangneung-Wonju National University, Gangwon-do 210-702, Republic of Korea. Electronic address: rotisong@gmail.com.
Min Ok
MO
Song
Nicholas School of the Environment, Box 90328, Duke University, Durham, NC 27708, USA. Electronic address: mmattie@agensys.com.
Michael D
MD
Mattie
Department of Biology, College of Natural Sciences, Gangneung-Wonju National University, Gangwon-do 210-702, Republic of Korea.
Chang-Ho
CH
Lee
Laboratory of Toxicology and Pharmacology, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA.
Jonathan H
JH
Freedman
D000818:Animals; D002478:Cells, Cultured; D003300:Copper / Q000494:pharmacology*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000187:drug effects*; D053263:Gene Regulatory Networks; D056945:Hep G2 Cells; D006801:Humans; D008668:Metallothionein / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000502:physiology*; D051266:Nuclear Respiratory Factor 1 / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic / Q000187:drug effects
D051267:NF-E2-Related Factor 2; C495636:Nfe2l2 protein, mouse; C495634:Nrf1 protein, mouse; D051266:Nuclear Respiratory Factor 1; C525355:metallothionein-1, mouse; D003300:Copper; D008668:Metallothionein
ARE; Copper; Metallothionein-1; Nrf1; Nrf2; Transcription