title: Identification of a novel proliferation-dependent C-rich element that mediates inhibition of the rat GLUT1 promoter.
abstract: Expression of the glucose transporter GLUT1 is high in proliferating and tumour cells. Conditions in which the transcriptional activity of GLUT1 promoter are maximal are characterized by the operation of activators such as Sp1 and inhibitors as Sp3. Here, we have identified an element at -67/-60 (C8 box) in the rat GLUT1 promoter to which nuclear factors bind in a proliferation-dependent manner. Competition studies with a series of mutated oligonucleotides suggest that these nuclear factors are different in the proliferative state and after confluence. The C8 element does not bind any of the known factors defined in databases. Mutation of the C8 sequence enhanced transcriptional activity of the GLUT1 promoter in 10T1/2 fibroblasts and in L6E9 myoblasts but not in myotubes. Furthermore, the functional activity of the C8 box is maximal in the presence of serum. In summary, we have identified a novel inhibitory element, C8 box, in the rat GLUT1 promoter that operates in a proliferation-dependent manner. In keeping with this view, serum enhances the inhibitory activity of the C8 box, suggesting that this is regulated by growth factors.
authors.affiliation: Parc Cientific de Barcelona and Departament de Bioquímica i Biologia Molecular, Facultat de Biologia, Universitat de Barcelona, Avda. Diagonal 645, E-08028 Barcelona, Spain.
authors.forename: Manuela
authors.initials: M
authors.lastname: Sánchez-Feutrie
authors.forename: Francesc
authors.initials: F
authors.lastname: Viñals
authors.forename: Manuel
authors.initials: M
authors.lastname: Palacín
authors.forename: Antonio
authors.initials: A
authors.lastname: Zorzano
mesh_terms: D000818:Animals; D001665:Binding Sites / Q000235:genetics; D002455:Cell Division / Q000235:genetics; D002460:Cell Line; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics / Q000378:metabolism; D003845:Deoxycytosine Nucleotides / Q000235:genetics; D024202:Electrophoretic Mobility Shift Assay; D005786:Gene Expression Regulation; D051272:Glucose Transporter Type 1; D009004:Monosaccharide Transport Proteins / Q000235:genetics*; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000378:metabolism; D032448:Myoblasts, Skeletal / Q000166:cytology / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D009841:Oligonucleotides / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011485:Protein Binding; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020218:Response Elements / Q000235:genetics*; D014162:Transfection
chemical_list: D003845:Deoxycytosine Nucleotides; D051272:Glucose Transporter Type 1; D009004:Monosaccharide Transport Proteins; D009687:Nuclear Proteins; D009841:Oligonucleotides; D011993:Recombinant Fusion Proteins; C495679:Slc2a1 protein, rat; D015500:Chloramphenicol O-Acetyltransferase