Positive and negative effects of nuclear receptors on transcription activation by AP-1 of the human choline acetyltransferase proximal promoter.
We have examined the 5'-flanking region (944 bp) of the human choline acetyltransferase (hChAT) gene for sequences that modulate its transcriptional activity and identified a sequence 5'-TGACCCA-3' which confers c-Jun/c-Fos (AP-1) inducibility of homologous and heterologous promoters. Using transient transfections in neuroblastoma NE-1-115 and COS-1 cells, we show that ligand-activated estrogen receptor (HEGo) represses the transcriptional activation by c-Fos/c-Jun. Testing HEGo mutants in transfection assays reveals that the ligand-binding domain is crucial for this repression, whereas the N-terminal (A/B) region and the DNA-binding domain are not essential. Gel retardation assays show that the hChAT AP-1 recognition sequence binds in vitro baculovirus-produced c-Jun/c-Fos proteins. This binding is inhibited by addition of baculovirus-produced HEGo. In contrast to HEGo, ligand-activated glucocorticoid, androgen, and retinoic acid receptors (RARs) enhance the transcription activation induced by c-Jun/c-Fos. All three types of RARs--RAR alpha, beta, gamma--and RXR alpha are able to stimulate AP-1 activity on the proximal hChAT promoter. Several mechanism possibilities involving protein-protein interaction are discussed to explain the phenomena.
Schmitt
M
M
Laboratoire de Génétique Moléculaire des Eucaryotes, CNRS-Unité 184, INSERM, Institut de Chimie Biologique de la Faculté de Médecine, Strasbourg, France.
Bausero
P
P
Simoni
P
P
Queuche
D
D
Geoffroy
V
V
Marschal
C
C
Kempf
J
J
Quirin-Stricker
C
C
D002478:Cells, Cultured; D002795:Choline O-Acetyltransferase / Q000235:genetics* / Q000502:physiology; D015870:Gene Expression; D006801:Humans; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D016760:Proto-Oncogene Proteins c-fos; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics* / Q000502:physiology; D017421:Sequence Analysis; D013256:Steroids; D018808:Transcription Factor AP-1; D014158:Transcription, Genetic / Q000235:genetics*
D016760:Proto-Oncogene Proteins c-fos; D018160:Receptors, Cytoplasmic and Nuclear; D013256:Steroids; D018808:Transcription Factor AP-1; D002795:Choline O-Acetyltransferase