| First Author | Rajakumar RA | Year | 1998 |
| Journal | J Biol Chem | Volume | 273 |
| Issue | 42 | Pages | 27474-83 |
| PubMed ID | 9765277 | Mgi Jnum | J:50345 |
| Mgi Id | MGI:1303197 | Doi | 10.1074/jbc.273.42.27474 |
| Citation | Rajakumar RA, et al. (1998) Sp1 and Sp3 regulate transcriptional activity of the facilitative glucose transporter isoform-3 gene in mammalian neuroblasts and trophoblasts. J Biol Chem 273(42):27474-83 |
| abstractText | The murine facilitative glucose transporter isoform 3 (Glut 3) is developmentally regulated and is predominantly expressed in neurons and trophoblasts. Employing the primer extension and RNase protection assays, the transcription start site (denoted as +1) of the murine Glut 3 gene was localized to 305 base pairs (bp) 5' to the ATG translation start codon. Transient transfection assays in N2A, H19-7 neuroblasts, and HRP.1 trophoblasts using sequential 5'-deletions of the murine Glut 3-luciferase fusion gene indicated that the -203 to +237 bp region with reference to the transcriptional start site contained promoter activity. Repressor function was limited to the -137 to -130 bp region within the transcriptional activation domain. The nuclear factors Sp1 and Sp3 bound this GC-rich region in N2A, H19-7, and HRP.1 cells. Dephosphorylation of Sp1 was essential for Glut 3 DNA binding. The related Sp3 protein also bound this same region of mouse Glut 3 in all three cell lines. Mutations of the Sp1-binding site employed in transient transfection and mobility shift assays confirmed the nature of the DNA-binding proteins, while supershift assays with anti-Sp1 and anti-Sp3 IgGs characterized the differences in the two DNA-binding proteins. Co-transfection of the Glut 3-luciferase fusion gene with or without mutations of the Sp1-binding site along with the Sp1 or Sp3 expression vectors in Drosophila SL2 cells confirmed a reciprocal effect, with Sp1 suppressing and Sp3 activating Glut 3 gene transcription. |
