Functional analysis of the rat cytochrome c oxidase subunit 6A1 promoter in primary neurons.

Cytochrome c oxidase (COX) is a multimeric enzyme consisting of 13 subunits that are encoded in both mitochondrial and nuclear genomes. We analyzed the promoter of the rat gene encoding the liver isoform of COX subunit VIa. Using transiently transfected primary neuronal cultures as a model system, we found that the basal promoter activity of this gene is localized to a region between positions -244 and +58 relative to the transcriptional start site. This region contains putative binding sites for the transcription factors Sp1, NRF-1, and NRF-2. Two of the NRF-2 sites in this basal promoter are organized in a tandem repeat. A deletion that disrupted this tandem repeat reduced transcription to approximately 25% of the basal level. Additional small deletion series and point mutation experiments confirmed the presence of two functional NRF-2 sites arranged in a tandem repeat, as well as a NRF-1 site and an Sp1 site. In vivo binding of NRF-2 to the rCOX6A1 promoter was confirmed with chromatin immunoprecipitation assay (ChIP). We conclude that Sp1, NRF-1, and NRF-2 are important in activating transcription of the rat COX6A1 gene.