The glucose-6-phosphatase catalytic subunit gene promoter contains both positive and negative glucocorticoid response elements.
Glucose-6-phosphatase catalyzes the final step in the gluconeogenic and glycogenolytic pathways. Glucocorticoids stimulate glucose-6-phosphatase catalytic subunit (G6Pase) gene transcription and studies performed in H4IIE hepatoma cells demonstrate the presence of a glucocorticoid response unit (GRU) in the proximal G6Pase promoter. In vitro deoxyribonuclease I footprinting analyses show that the glucocorticoid receptor binds to three glucocorticoid response elements (GREs) in the -231 to -129 promoter region and transfection results indicate all three contribute to glucocorticoid induction of G6Pase gene transcription. Furthermore, binding sites for hepatocyte nuclear factor-1 and -4, CRE binding factors, and FKHR (FOXO1a) are required for the full glucocorticoid response. Chromatin immunoprecipitation assays show that dexamethasone treatment stimulates glucocorticoid receptor and FKHR binding to the endogenous G6Pase promoter. Surprisingly, although glucocorticoids stimulate G6Pase gene transcription, deoxyribonuclease I footprinting and transfection analyses demonstrate the presence of a negative GRE and an associated negative accessory factor element in the -271 to -225 promoter region, which inhibit the glucocorticoid response. This appears to be the first report of a promoter that contains both positive and negative GREs, which function within the same cellular environment. We hypothesize that targeted signaling to the negative accessory element within the GRU may provide tight regulation of the glucocorticoid stimulation.
Vander Kooi
Beth T
BT
Department of Molecular Physiology and Biophysics, 761 PRB (MRB II), Vanderbilt University Medical School, Nashville, TN 37232-0615, USA.
Onuma
Hiroshi
H
Oeser
James K
JK
Svitek
Christina A
CA
Allen
Shelley R
SR
Vander Kooi
Craig W
CW
Chazin
Walter J
WJ
O'Brien
Richard M
RM
D000818:Animals; D001483:Base Sequence; D002384:Catalysis; D003907:Dexamethasone / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic; D017930:Genes, Reporter / Q000235:genetics; D005938:Glucocorticoids / Q000378:metabolism* / Q000494:pharmacology; D005952:Glucose-6-Phosphatase / Q000235:genetics*; D051379:Mice; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics; D021122:Protein Subunits / Q000235:genetics; D051381:Rats; D011965:Receptors, Glucocorticoid / Q000378:metabolism; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics; D020218:Response Elements / Q000187:drug effects / Q000235:genetics*; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic
D005938:Glucocorticoids; D021122:Protein Subunits; D011965:Receptors, Glucocorticoid; D014157:Transcription Factors; D003907:Dexamethasone; D005952:Glucose-6-Phosphatase