On the role of the general transcription factor Sp1 in the activation and repression of diverse mammalian oxidative phosphorylation genes

To gain insight into the role of the general transcription factor, Spl, in the expression of nuclear genes involved in mitochondrial biogenesis, we in vestigated Spl activation of the adenine nucleotide translocator 2, cytochr ome c(1), F-1-ATPase beta subunit, and the mitochondria transcription facto r (mtTFA) promoters transfected into Drosophila cell lines. The numbers and organization of GC elements vary in the four promoters, but the magnitude of activation by coexpressed human Sp1 was similar. A feature common to the four promoters is the presence of multiple, proximal Sp1-activating elemen ts that account for 50% or more of the transcription activation by Sp1. The distribution and function of individual distal Sp1 elements is less define d and appear to be more promoter-specific. Finally, data from transfected D rosophila cells provide the first direct proof for the involvement of Sp1 i n the negative regulation of the ANT2 promoter and as a possible participan t in repression of the beta-subunit promoter. The role of Spl in both the p ositive and negative regulation of OXPHOS promoters is unique.