Sp3 and Sp4 can repress transcription by competing with Sp1 for the core cis-elements on the human ADH5/FDH minimal promoter

The human alcohol dehydrogenase 5 gene (also known as the formaldehyde dehy drogenase gene, ADH5/FDH) has a CC-rich promoter with many sites at which t ranscription factors bind. A minimal promoter extending from -34 base pairs (bp) to +61 bp directs high levels of transcription in several different c ells, consistent with the ubiquitous expression of the gene. Nearly the ent ire minimal promoter can be bound by Spl, We analyzed the transcriptional r egulation of ADH5/FDH by members of the Spl multigene family. Two core cis- elements (-22 bp to +22 bp) had the highest affinity for Spl, Mutagenesis r evealed that these cis-elements are critical for transcriptional activation . The zinc-finger domains of Sp3 and Sp4 also bind selectively to the core cis-elements. In Drosophila SL2 cells, which lack endogenous Spl, the minim al promoter cannot drive transcription. Introduction of Spl activated trans cription over 50-fold, suggesting that Spl is critical in the initiation of transcription. Neither Sp3 nor Sp4 was able to activate transcription in t hose cells, and transcriptional activation by Spl was repressed by Sp3 or S p4, These data suggest that Sp3 and Sp4 can repress transcription by compet ing with Spl for binding to the core cis-elements, The content of Spl, Sp3, and Sp4 in different cells may be critical factors regulating transcriptio n of the ADH5/FDH gene.