Heme activates the heme oxygenase-1 gene in renal epithelial cells by stabilizing Nrf2.
The mechanism of heme oxygenase-1 gene (ho-1) activation by heme in immortalized rat proximal tubular epithelial cells was examined. Analysis of the ho-1 promoter identified the heme-responsive sequences as the stress-response element (StRE), multiple copies of which are present in two enhancer regions, E1 and E2. Electrophoretic mobility shift assays identified Nrf2, MafG, ATF3, and Jun and Fos family members as StRE-binding proteins; binding of Nrf2, MafG, and ATF3 was increased in response to heme. Dominant-negative mutants of Nrf2 and Maf, but not of c-Fos and c-Jun, inhibited basal and heme-induced expression of an E1-controlled luciferase gene. Heme did not affect the transcription activity of Nrf2, dimerization between Nrf2 and MafG, or the level of MafG, but did stimulate expression of Nrf2. Heme did not influence the level of Nrf2 mRNA but increased the half-life of Nrf2 protein from approximately 10 min to nearly 110 min. These results indicate that heme promotes stabilization of Nrf2, leading to accumulation of Nrf2. MafG dimers that bind to StREs to activate the ho-1 gene.
Alam
Jawed
J
Department of Molecular Genetics, Ochsner Clinic Foundation, New Orleans 70121, USA. jalam@ochsner.org
Killeen
Erin
E
Gong
Pengfei
P
Naquin
Ryan
R
Hu
Bin
B
Stewart
Daniel
D
Ingelfinger
Julie R
JR
Nath
Karl A
KA
D000818:Animals; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D005799:Genes, Dominant; D006418:Heme / Q000494:pharmacology*; D006419:Heme Oxygenase (Decyclizing) / Q000235:genetics*; D051547:Heme Oxygenase-1; D007687:Kidney Tubules, Proximal / Q000166:cytology; D051259:MafG Transcription Factor; D051267:NF-E2-Related Factor 2; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D020218:Response Elements / Q000502:physiology; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*
D004268:DNA-Binding Proteins; D051259:MafG Transcription Factor; C491246:Mafg protein, rat; D051267:NF-E2-Related Factor 2; C495637:Nfe2l2 protein, rat; D012333:RNA, Messenger; D012097:Repressor Proteins; D015534:Trans-Activators; D006418:Heme; D006419:Heme Oxygenase (Decyclizing); D051547:Heme Oxygenase-1