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)

We produced transgenic mice carrying about 3 kb of the 5'-flanking sequence of the rat pyruvate kinase L gene linked to the chloramphenicol acetyltransferase (CAT) structural gene. Expression of the transgene was observed only in tissues in which the endogenous L-type pyruvate kinase is expressed. Dietary glucose or insulin induced similar increases in the levels of CAT and L-type pyruvate kinase mRNAs in the liver. However, the fructose-induced level of CAT mRNA was about 3- and 6- fold lower than those of endogenous L-type pyruvate kinase mRNA in the liver and kidney, respectively, confirming our previous finding that stabilization of the transcripts of the pyruvate kinase L gene is an important regulatory step in fructose induction, especially in the kidney. Thus we conclude that all the cis-acting elements responsible for tissue-specific expression of the L-type pyruvate kinase and its stimulation by dietary components and insulin are localized in the sequence from about nucleotide -3000 to +37 in the pyruvate kinase L gene.
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PMID:Tissue-specific expression of rat pyruvate kinase L/chloramphenicol acetyltransferase fusion gene in transgenic mice and its regulation by diet and insulin. 220 46

The rat pyruvate kinase L (PKL) gene produces the L- and R-type isozymes by alternative transcription that is regulated in a tissue-specific manner. To investigate which DNA elements are involved in hepatocyte-specific expression of the L-type isozyme, we performed transient DNA transfer experiments with PKL/chloramphenicol acetyltransferase fusion genes. We found three positive regulatory regions required for expression of the L-type isozyme in adult rat hepatocytes by functional analyses of a series of 5' and internal deletion constructs of the fusion genes. These regions, designated as PKL-I, PKL-II, and PKL-III, were located between nucleotides -76 and -94, -126 and -149, and -150 and -170, respectively. PKL-I showed enhancer-like activity alone, whereas PKL-II and PKL-III did not have any independent effect. Combinations of L-I + L-II and L-II + L-III, but not of L-I + L-III, showed synergistic enhancer activities when oriented in the same direction. The inclusion of all three elements oriented in the same direction had the maximum synergistic effect, indicating that these elements function as a unit. This unit enhanced expression from heterologous as well as homologous promoters in a manner that was independent of its orientation and position relative to the cap site. The activity of the unit was not detected in HeLa cells or K562 erythroleukemia cells, suggesting that this unit possessed cell-type specificity. PKL-I consists of a palindrome sequence 5'-CTGGTTATACTTTAACCAG-3', which contain a sequence homologous to the LF-B1-binding site. PKL-II contains the sequence 5'-TTCCTGGACTCTGGCCCCCAGTGT-3', which is similar to that of the LF-A1-binding site. PKL-III contains a palindrome sequence 5'-CCACGGGGCACTCCCGTGG-3', which include a sequence homologous to the binding site of the adenovirus major late transcription factor. Gel retardation assay indicated that the different trans-acting factors interacted with three elements and that the transacting protein bound to PKL-I was in fact LF-B1. However, the trans-acting factors bound to PKL-II and PKL-III were different from LF-A1 and major late transcription factor, respectively. Thus, we conclude that three cis-acting elements are very important for specific expression of the PKL gene in hepatocytes and that LF-B1 and two unknown factors bound to these elements interact with each other to cause a synergistic effect.
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PMID:Identification and characterization of hepatocyte-specific regulatory regions of the rat pyruvate kinase L gene. The synergistic effect of multiple elements. 224 64

The L-II element (-149 to -126 bp) in the enhancer unit of the rat pyruvate kinase L (PKL) gene is required for cell-type-specific transcription and induction by carbohydrates. This element was found to bind multiple nuclear proteins with different heat stabilities. A heat-labile factor was shown to be hepatocyte nuclear factor (HNF) 4 by the electrophoretic mobility-shift assay (EMSA) using various competitor DNAs and anti-HNF4 serum. A heat-stable factor was purified from rat liver nuclear extract and was resolved as two protein bands migrating at about 33 kDa on SDS/polyacrylamide gels. Peptide sequence analysis revealed that these proteins were nuclear factor (NF) 1-L and NF1/Red1. The heat-stable factor was also identified as a member of the NF1 family by using various competitor DNAs and anti-NF1 serum in an EMSA. In addition, we found that a factor bound to the accessory site of the rat S14 gene, which is necessary for carbohydrate responsiveness of this gene, was also a member of the NF1 family, raising the possibility that the NF1 family is involved in the carbohydrate regulation of gene transcription by interactions with other proteins. The NF1 family members and HNF4 interacted with overlapping sequences of the L-II element, wherein the 5' half-site was more critical for NF1 binding, and the 3' site was more important for HNF4 binding. Co-transfection of a vector expressing either NF1-L or NF1/Red1 repressed the transcription of the PKL enhancer unit-chloramphenicol acetyltransferase (CAT) fusion gene in HepG2 cells, whereas co-transfection of a vector expressing HNF4 activated the transcription of the same reporter gene. Furthermore NF1 family members antagonized the effect of HNF4 on PKL enhancer unit-CAT fusion gene expression when both expression plasmids were co-transfected. We conclude that NF1 family members and HNF4 regulate transcription of the PKL gene in an opposing manner by binding overlapping sequences of the L-II element.
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PMID:Members of the nuclear factor 1 family and hepatocyte nuclear factor 4 bind to overlapping sequences of the L-II element on the rat pyruvate kinase L gene promoter and regulate its expression. 921 Apr 17