Abstract
The liver-type and muscle-type isozymes of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase are encoded by one gene that uses two alternative promoters. We have identified cis-acting sequences and protein-binding sites on the liver-type promoter. Transfection assays with deleted promoters showed that maximal promoter activity is contained within 360 bp upstream of the cap site. DNase I footprinting experiments with liver and spleen nuclear extracts and with purified proteins revealed several protein-binding sites in this region. These included four binding sites for nuclear factor I, one site that contains an octamer consensus but showed a liver-specific footprint pattern, two liver-specific protein-binding sites, and one poly(dG)-containing binding site. Transfection of cells of hepatic origin suggested that all these sites except one are involved in transcriptional regulation. The region between -360 and -2663 contained an element that functioned as a silencer in a nonhepatic cell line. We conclude that in liver transcription from the liver-type promoter of the 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase gene is controlled by ubiquitous and tissue-specific factors and involves activating and derepressing mechanisms.
Highlights
Hormone and Metabolic Research Unit, Louvain University Medical School and International Institute of Cellular and Molecular Pathology, 75 Avenue Hippocrate, B-1200 Brussels, Belgium
We found that full promoter activity in transfection experiments is conferred by the 360 bp upstream from the cap site
We have demonstrated in vitro DNA-protein interactions on the L promoter of the gene encoding the L and M PFK-2/FBPase-2 isozymes and have delineated by transfection some of its transcriptional regulatory elements
Summary
The liver-type and muscle-type isozymes of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase are encoded by one gene that uses two alternative promoters. DNase I footprinting experiments with liver and spleen nuclear extracts and with purified proteins revealed several protein-binding sites in this region. We conclude that in liver transcription from the liver-type promoter of the 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase gene is controlled by ubiquitous and tissue-specific factors and involves activating and derepressing mechanisms. The synthesis and degradation of fructose-2,6-bisphosphate are catalyzed, respectively, by 6-phosphofructo-2-kinase (PFK-2) and fructose-2,6-bisphosphatase (FBPase-2). In liver these two activities are borne by separate domains of a homodimeric protein which is one ofthe rare bifunctional enzymes. The PFK-2/ FBPase-2 L promoter is an interesting model for studying the tissue-specific and hormonal regulation of transcription. The factors that bind to these sequences have been identified by in vitro DNase I footprinting and band-shift assays
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
