Analysis of a repressor region in the human neuropeptide Y gene that binds Oct-1 and Pbx-1 in GT1-7 neurons

Abstract

The mechanisms dictating the developmental expression of individual neuropeptides within the hypothalamus have not yet been elucidated. In this paper we have studied the cis-acting elements involved in the repression of neuropeptide Y (NPY) gene expression in a gonadotropin-releasing hormone (GnRH) neuronal cell model, GT1-7 cells. Using transient transfection of the human NPY 5 ′ regulatory region into the GT1-7 neurons, we have found a repressor region located between −867 and −1078. DNase I footprint analysis of this region revealed three specific protein binding elements. Further analysis of the region between −942 and −922 bp using electrophoretic mobility shift assays revealed that four different transcription factor-DNA complexes form with GT1-7 nuclear proteins, whereas only three complexes are detected using baby hamster kidney (BHK) cell nuclear extract. Mutation of the consensus binding sequence abolishes all complex formation on the −924/−922 oligonucleotide. Antibody supershift assays revealed that Oct-1 and Pbx-1 antibodies were able to eliminate the appearance of two specific complexes. Therefore we suggest that this region may be important for transcriptional repression of the NPY gene in a heterologous cell model, through complex, coordinate protein–protein interactions.