Is nuclear respiratory factor 2 a master transcriptional coordinator for all ten nuclear-encoded cytochrome c oxidase subunits in neurons?
Cytochrome c oxidase (COX), the terminal enzyme of the mitochondrial electron transport chain, is a multi-subunit, bigenomically encoded inner mitochondrial membrane protein. Of the thirteen subunits, three are encoded in the mitochondrial genome and ten others are encoded in the nuclear genome. Transcriptional coordination of nuclear-encoded COX subunit genes is likely accomplished by transcription factors responding to upstream signals. Previous studies have found that nuclear-encoded COX subunit genes are under the control of specific transcription factors, such as nuclear respiratory factor 2 (NRF-2). However, it is not known if a single transcription factor binds to all ten of COX subunit promoters. In the current study, we identified in silico putative NRF-2 binding sites on all ten nuclear-encoded COX gene promoters in the rat genome. Chromatin immunoprecipitation assay showed that NRF-2 bound in vivo to six of the ten nuclear-encoded COX subunit promoters. Electrophoretic mobility supershift assays demonstrated binding of NRF-2 to the other four subunits, and promoter mutation study confirmed the functionality of these NRF-2 binding sites. Finally, transfection of dominant-negative constructs of NRF-2 proteins caused a significant reduction of COX expression. We conclude that NRF-2 is an important mediator of coordinated regulation of all ten nuclear-encoded COX subunit genes in neurons.
Ongwijitwat
Sakkapol
S
Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA.
Wong-Riley
Margaret T T
MT
D000818:Animals; D000831:Animals, Newborn; D001483:Base Sequence; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000378:metabolism*; D047369:Chromatin Immunoprecipitation; D003576:Electron Transport Complex IV / Q000235:genetics / Q000378:metabolism*; D051268:GA-Binding Protein Transcription Factor / Q000378:metabolism*; D005786:Gene Expression Regulation; D005799:Genes, Dominant; D008969:Molecular Sequence Data; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011485:Protein Binding; D051381:Rats; D012045:Regulatory Sequences, Nucleic Acid; D014162:Transfection
D051268:GA-Binding Protein Transcription Factor; D003576:Electron Transport Complex IV