PROMOTER ANALYSIS OF THE HUMAN SUCCINATE-DEHYDROGENASE IRON-PROTEIN GENE - BOTH NUCLEAR RESPIRATORY FACTORS NRF-1 AND NRF-2 ARE REQUIRED

The iron-sulfur subunit of succinate dehydrogenase is one of the four subunits of complex II of the mitochondrial electron transport chain. Its gene, SDH2, is one of the four nuclear-encoded genes for this comp lex. Reporter gene analysis of the human SDH2 promoter indicates that it is transcriptionally regulated by the nuclear respiratory factors N RF-1 and NRF-2, Their binding sites reside immediately upstream (withi n 90 bp) of the transcription start site. Site-directed mutagenesis of either site lowers the reporter gene activity by tenfold to a basal l evel. Gel shift experiments and competition experiments with the authe ntic NRF-1 and NRF-2 DNA oligomers from previously characterized nucle ar respiratory genes strengthen the proposed role of these two transcr iptional regulators. These experiments extend the proposed regulatory role of these two transcription factors to complex IT of the respirato ry chain. The expression of three of the four genes of complex II was also examined when mouse myoblast C2C12 cells were induced to differen tiate into myotubes. Up-regulation upon differentiation in tissue cult ure is only modest, 2-3 fold over the myoblast cells.