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)

Somatotropin (ST) markedly decreases lipogenesis, fatty acid synthase (FAS) enzyme activity and mRNA abundance in pig adipocytes. The present study was conducted to determine whether the decrease in FAS mRNA in 3T3-F442A adipocytes was the result of a decrease in transcription of the FAS gene and/or a change in FAS mRNA stability. Insulin increased the abundance of FAS mRNA 2-13-fold and fatty acid synthesis 3-7-fold. Somatotropin decreased the stimulatory effect of insulin on the abundance of FAS mRNA and lipogenesis by 40-70% and 20-60% respectively. Subsequent run-on analyses demonstrated that the decrease observed in FAS mRNA in response to ST was associated with an 82% decrease in transcription; ST significantly shortened the half-life of FAS mRNA from 35 to 11 h. To corroborate the run-on analyses, cells were stably transfected with a pFAS-CAT5 (in which CAT stands for chloramphenicol acetyltransferase) reporter construct that contained 2195 bp of the 5' flanking region of the rat FAS gene. Insulin treatment increased FAS-CAT activity 4.7-fold. When ST was added to the insulin-containing medium there was an approx. 60% reduction in FAS-CAT activity. In summary, our results indicate that ST decreases FAS mRNA levels and that this is the result of a marked decrease in both transcription of the FAS gene and stability of the FAS mRNA.
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PMID:Somatotropin-dependent decrease in fatty acid synthase mRNA abundance in 3T3-F442A adipocytes is the result of a decrease in both gene transcription and mRNA stability. 956 Mar 9

Somatotropin (ST) antagonizes insulin stimulation of fatty acid synthase (FAS) enzyme activity and gene transcription in adipocytes. Previous studies have shown that an insulin response element (IRE) is located in the proximal region of the FAS promoter (-71 to -50) and upstream stimulatory factor (USF) 1 binds to this IRE. The present study was conducted to initially evaluate whether there is a somatotropin response element (STRE) in the 5'flanking region of the FAS gene and to determine whether USF1 mediates the effect of ST on FAS gene transcription in 3T3-F442A adipocytes. Two 5' deletion FAS promoter constructs (pFAS-CATS4 and pFAS-CAT5), which contain the 5' flanking sequences of the rat FAS gene at -112 to +65 and -2195 to +65, respectively, were stably transfected into 3T3-F442A preadipocytes. Insulin stimulated chloramphenicol acetyltransferase (CAT) activity 1.7- and 4.7-fold (P < 0.05) in 3T3-F442A adipocytes transfected with pFAS-CATS4 and pFAS-CAT5, respectively. In contrast, bovine somatotropin (bST) attenuated the stimulatory effect of insulin on CAT activity by approximately 60% (P < 0.05) in both constructs. When 3T3-F442A adipocytes were treated with insulin (10 ng/mL) or insulin (10 ng/mL) plus bST (100 ng/mL) for 24, 48, or 72 h, neither insulin nor bST significantly affected USF1 mRNA levels. When human USF1 (hUSF1) cDNA probe was used, however, insulin increased the abundance of an unidentified transcript (named hUSF1-like mRNA) 11- to 25-fold (P < 0.05) and ST decreased the stimulatory effect of insulin on hUSF1-like mRNA levels by 50 to 90% (P < 0.05). Western blot analyses of nuclear extracts from cells treated with insulin (10 ng/mL) or insulin (10 ng/mL) plus bST (100 ng/mL) for 48 h demonstrated that the abundance of USF1 was not affected by insulin or ST. Furthermore, electrophoretic mobility shift analyses (EMSA) of nuclear extracts revealed that neither insulin nor ST had an effect on the binding of USF1 to the IRE. These results suggest that a STRE may be located within the first 112 bp of the FAS promoter and that USF1 does not directly mediate the effect of ST on transcription of the FAS gene in 3T3-F442A adipocytes.
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PMID:Transcriptional regulation of fatty acid synthase gene by somatotropin in 3T3-F442A adipocytes. 1158 20