Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.3.9 (glucose-6-phosphatase)
 3,081 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Summary. Insulin is known to inhibit glucose-6-phosphatase gene expression through PI 3-kinase/PKB mediated phosphorylation and inactivation of the forkhead transcription factor FKHR, which is a potent transactivator of the glucose-6-phosphatase gene. To study the function and regulation of the transcription factor FKHR in hepatic cells, we constructed a hydroxytamoxifen-inducible version of FKHR by fusing a part of the hormone binding domain of the estrogen receptor (ER) to the C-terminus of FKHR (FKHR-ER). In HepG2-cells transiently transfected with plasmids encoding the FKHR-ER fusion protein and a glucose-6-phosphatase reporter construct, hydroxytamoxifen induced a marked induction of glucose-6-phosphatase promoter activity, whereas no effect was observed in control cells. We next generated a H4IIEC3 rat hepatoma cell line stably expressing both FKHR-ER and a glucose-6-phosphatase promoter-based reporter construct. After 2h stimulation with hydroxytamoxifen, the promoter activity was stimulated 3-5 fold, and continued to increase up to 100-fold after 15 h. The response was half maximal at 0.5 microM hydroxytamoxifen. Insulin (1 nM) decreased the hydroxytamoxifen induced promoter activity by about 70% of the maximal response. This cell system can be used for (1) the identification of FKHR dependent genes and for (2) high throughput screening (HTS) of agents affecting the activity of FKHR and its regulation by insulin. Abbreviations used: FKHR, forkhead in rhabdomyosarcoma; G6Pase, glucose-6-phosphatase; PKB, protein kinase B; PI 3-kinase, phosphatidyl-inositol 3-kinase; IRU, insulin-responsive unit; Tx, 4-hydroxytamoxifen, ER, estrogen receptor; HBD, hormone binding domain
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PMID:Construction and characterization of a conditionally active construct of the insulin-regulated forkhead transcription factor FKHR. 1237 35

Islet-specific glucose-6-phosphatase (G6Pase) catalytic-subunit-related protein (IGRP) is a homologue of the catalytic subunit of G6Pase, the enzyme that catalyses the final step of the gluconeogenic pathway. The analysis of IGRP-chloramphenicol acetyltransferase (CAT) fusion-gene expression through transient transfection of islet-derived beta TC-3 cells revealed that multiple promoter regions, located between -306 and -97, are required for maximal IGRP-CAT fusion-gene expression. These regions correlated with trans -acting factor-binding sites in the IGRP promoter that were identified in beta TC-3 cells in situ using the ligation-mediated PCR (LMPCR) footprinting technique. However, the LMPCR data also revealed additional trans -acting factor-binding sites located between -97 and +1 that overlap two E-box motifs, even though this region by itself conferred minimal fusion-gene expression. The data presented here show that these E-box motifs are important for IGRP promoter activity, but that their action is only manifest in the presence of distal promoter elements. Thus mutation of either E-box motif in the context of the -306 to +3 IGRP promoter region reduces fusion-gene expression. These two E-box motifs have distinct sequences and preferentially bind NeuroD/BETA2 (neurogenic differentiation/beta-cell E box transactivator 2) and upstream stimulatory factor (USF) in vitro, consistent with the binding of both factors to the IGRP promoter in situ, as determined using the chromatin-immunoprecipitation (ChIP) assay. Based on experiments using mutated IGRP promoter constructs, we propose a model to explain how the ubiquitously expressed USF could contribute to islet-specific IGRP gene expression.
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PMID:Upstream stimulatory factor (USF) and neurogenic differentiation/beta-cell E box transactivator 2 (NeuroD/BETA2) contribute to islet-specific glucose-6-phosphatase catalytic-subunit-related protein (IGRP) gene expression. 1254 Feb 93