The role of Sp2, Sp3 and Sp4 in the trascriptional regulation of the promoter of nuclear encoded mitochondrial genes

Abstract EN

The GC-box is an important transcriptional regulatory element present in the promoters of many mammalian genes, and is found in most, if not all, oxidative phosphorylation (OXPHOS) promoters.

In the present study we examine the effects of three Sp1 family members (Sp2, Sp3, and Sp4) on the adenine nucleotide translocate 2, cytochrome c1, F1-ATPase -subunit, and the mitochondria transcription factor (mt TFA) promoters in Drosophila SL2 cell line.

Sp3, like Sp1, strongly activates transcription all four promoters.

SP4 stimulates, moderately, but Sp2 had no effect.

In addition, Sp3 can, like Sp1, inhibit transcription from the proximal promoter of the ANT2 gene through binding to the Cbox GC element.

By contrast, Sp4 and Sp2 do not repress promoter activity.

Furthermore, since Sp4 and Sp2 bind to the Cbox repression element on the ANT2 promoter, but do not repress transcription, inhibition of transcription cannot be explained by steric hindrance of pre-initiation complex assembly.

These data suggest that different Sp1 family members differentially affect transcription from the OXPHOS promoters.