Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.3.1.28 (chloramphenicol acetyltransferase)
 5,100 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The promoter of the gene coding for the rat cytosolic aspartate aminotransferase was cloned from a Charon 4A genomic library. We have sequenced a 1.1-kilobase PstI-PstI fragment which contains the first exon of the gene, the beginning of the first intron and 682 base pairs of the 5' regulatory region (+1 being the A of the first ATG codon), which exhibits promoter activity. The promoter region is G + C rich, does not include any TATA-like element, but has 4 putative Sp1-binding sites and 6 regularly spaced CCAAT boxes. The promoter activity of the 5' regulatory region, as well as its sensitivity to glucocorticoids, were assessed by transient gene expression assays after fusion to the chloramphenicol acetyltransferase gene in the hepatoma cell lines HepG2 and Fao. Multiple transcription start sites were found on the gene over a short distance (55 base pairs), but they were differentially regulated by glucocorticoids as determined by both primer extension analysis and S1 mapping. In particular, transcription from 2 start sites was increased 15- to 18-fold, whereas transcription from the 3 other ones was increased 3-fold. In addition, three new start sites, below the detection limit in control cells, were highly induced. Therefore, a hormonal regulatory element can discriminate among closely related transcription start sites.
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PMID:Hormonal discrimination among transcription start sites of aspartate aminotransferase. 230 72

The regulation of cytosolic aspartate aminotransferase (cAspAT) gene expression by phorbol esters was investigated in the highly differentiated hepatoma cell line Fao. Phorbol 12,13-dibutyrate (PdBu) had no effect on basal activity but partially inhibited the induction of cAspAT by dexamethasone. The extent of inhibition (40%) was similar to that obtained with insulin or vanadate. The inhibitory effects of PdBu and vanadate were additive. In the case of PdBu, the inhibitory effects could be eliminated by first incubating the cells with PdBu, which down-regulates protein kinase C. In contrast, inhibition by insulin was not modified by this treatment. The molecular mechanism of PdBu action was investigated. Northern blot analysis showed that the steady-state mRNA levels of cAspAT were decreased by PdBu in the presence of dexamethasone. In addition, the transcription rate, as measured by run-on experiments, was also decreased under the same conditions. Finally, a 2.4 kb promoter fragment driving the chloramphenicol acetyltransferase gene was stably transfected into the Fao cells. The regulation of the activity of this promoter fragment by dexamethasone and PdBu was similar to the regulation of the endogenous cAspAT activity. We conclude that PdBu acts by regulating the promoter activity of the cAsPAT gene.
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PMID:Phorbol esters inhibit the glucocorticoid-mediated stimulation of cytosolic aspartate aminotransferase gene transcription. 811 Jan 86

Cytosolic aspartate aminotransferase (cAspAT) participates in gluconeogenesis in the liver and is expected to exert a glyceroneogenic function in the adipose tissue when the supply of glucose is limited. Here we demonstrate that adipose cAspAT messenger RNA (mRNA) is increased when rats are fed a low carbohydrate diet. In the 3T3-F442A, BFC-1 adipocyte cell lines and differentiated adipocytes in primary culture, a 24 h glucose deprivation induces approximately a 4-fold increase in cytosolic AspAT (cAspAT) mRNA, whereas mitochondrial AspAT mRNA remains unchanged. cAspAT activity is also increased in a weaker but reproducible manner. Addition of glucose within a physiological range of concentrations reverses the increase of cAspAT mRNA in 8 h (EC50 = 1.25 g/liter). Such a regulation requires protein synthesis and is specific for adipocytes differentiated in culture. It does not occur in Fao or H4IIE hepatoma cells, in C2 muscle cells, or in 293 kidney cells. 2-deoxyglucose mimicks glucose, while 3-orthomethyl-glucose has no effect, suggesting that glucose-6-phosphate is the effector. cAspAT mRNA stability is not affected by glucose deprivation. To ascertain the transcriptional nature of the glucose effect, we have stably transfected 3T3-F442A adipoblasts with constructs containing the chloramphenicol acetyltransferase reporter gene under the control of either 5'-deletions of the cAspAT gene promoter or internal fragments in an heterologous context. We demonstrate that a glucose response element(s) is present in the region between -1838 and -1702 bp relative to the translation start site. In this region, three DNA sequences bind nuclear proteins from adipocytes as shown by footprinting experiments. Our results indicate that cAspAT gene transcription is repressed by glucose selectively in adipocytes.
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PMID:Identification of an adipocyte-specific negative glucose response region in the cytosolic aspartate aminotransferase gene. 983 31

Prolactin stimulates citrate accumulation in prostate cells by increasing the expression of mitochondrial aspartate aminotransferase (mAAT). In this study, we further investigated the mechanism of prolactin regulation of mAAT expression in rat lateral prostate and LNCaP and PC-3 prostate cancer cells. Prolactin and 12-O-tetra-decanoylphorbol 13-acetate (TPA) increased the mAAT mRNA level twofold to fourfold. In addition, prolactin and TPA increased protein kinase C (PKC) activity in prostate cells 20% to 60% and 40% to 210%, respectively. The effects of both prolactin and TPA on mAAT mRNA were eliminated by downregulation of PKC. The effect of prolactin and TPA on gene transcription was determined using mAAT-chloramphenicol acetyltransferase (CAT) reporter-gene constructs, transiently transfected into PC-3 cells. The 59 untranslated region of the precursor form (pmAAT) of the mAAT gene contains five sequences that are homologous to the consensus TPA response elements (TRE). Reporter constructs with various combinations of these sequences were used to assay prolactin stimulation of CAT transcription in PC-3 cells. Prolactin increased CAT expression in PC-3 cells transfected with a reporter gene containing four of the TRE consensus sequences. Another CAT reporter gene, which contained two of the putative TREs, was also stimulated by prolactin, but a third reporter, containing the two other TRE sequences, was not induced by prolactin. These results suggest that prolactin regulates mAAT at the transcriptional level. Moreover, because both prolactin and TPA induced PKC activity, and because the effects of prolactin and TPA were eliminated when PKC was downregulated, we postulate that the prolactin effect on mAAT expression is mediated via the diacylglycerol PKC signal transduction pathway in rat lateral prostate and human prostate cancer cells.
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PMID:Protein Kinase C Mediates Prolactin Regulation of Mitochondrial Aspartate Aminotransferase Gene Expression in Prostate Cells. 1085 Dec 92