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)

Prolonged depolarization has been used as a model of adaptive changes in the expression of various proteins, such as ion channels and neurotransmitter biosynthetic enzymes, in response to increased trans-synaptic activity in the nervous system. In depolarized PC12 cells, tyrosine hydroxylase (TH) mRNA levels increased severalfold (Kilbourne, E. J., and Sabban, E. L. (1990) Mol. Brain Res. 8, 121-127). In this study, membrane depolarization caused an increase in the expression of the reporter gene chloramphenicol acetyltransferase (CAT), under transcriptional control of the 5' region of the rat TH gene. These results indicate that membrane depolarization leads to increased transcription of the TH gene. Protein kinase C inhibitors had no effect on the induction of TH mRNA by depolarization, as well as the increase in formation of CAT under control of the upstream region of the TH gene. The depolarization responsive element in the TH gene was mapped to the region containing the cAMP responsive element. This region of the TH gene also increased CAT activity in response to the calcium ionophore, ionomycin. Interestingly, combined treatment with cAMP analogs and membrane depolarization had a greater effect than either alone on TH mRNA levels, as well as on CAT activity in PC12 cells transfected with the plasmid containing the cAMP responsive element.
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PMID:Regulated expression of the tyrosine hydroxylase gene by membrane depolarization. Identification of the responsive element and possible second messengers. 134 5

The oxygen-dependent promoter of the Vitreoscilla hemoglobin (VHb) gene has been shown to be functional in E. coli. Earlier studies established that the promoter is maximally induced under microaerobic conditions and that its activity is also influenced by the cAMP-CAP complex. We demonstrate here that the promoter can be used for regulated, high-level expression of recombinant proteins in two-stage fed-batch fermentations. The promoter is maximally induced at dissolved oxygen levels lower than 5% air saturation. Despite the influence of catabolite repression, glucose and glycerol-containing media give comparable product levels under carbon-limited conditions such as those encountered in typical fed-batch fermentations. The possibility of a third level of control of promoter activity is also indicated. This mode of induction can be repressed by addition of a complex nitrogen source such as yeast extract to the medium. The observed promoter activity can be modulated at least 30-fold over the course of high-cell density fermentations producing either cloned beta-galactosidase or cloned chloramphenicol acetyltransferase (CAT). Densitometer scanning of SDS-polyacrylamide gels revealed that beta-galactosidase was expressed to a level of approximately 10% of total cellular protein.
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PMID:Expression of recombinant proteins in Escherichia coli using an oxygen-responsive promoter. 136 36

During continuous stimulation by agonist, beta 1- and beta 2-adrenergic receptors (ARs) undergo processes that lead to decreases in receptor expression. This receptor down-regulation serves to limit the cellular cAMP response during chronic agonist exposure. In the recently described third subtype of the beta AR, denoted beta 3AR, we found four potential cAMP response elements in the 5' flanking region, suggesting that expression of this receptor might be positively regulated by agonists. These elements were cloned into the vector pA10CAT2, which contains a chloramphenicol acetyltransferase reporter gene, and transiently expressed in VERO cells. Three of these elements, TGACTCCA, TGAGGTCT, and CGAGGTCA (located 518, 622, and 1125 bases upstream of the beta 3AR coding block, respectively) were found to increase transcription of the chloramphenicol acetyltransferase gene in response to cAMP analogues and agents that increase intracellular cAMP. 3T3-F442A cells, when differentiated into the adipocyte phenotype by insulin, expressed beta 3AR, and nuclear runoff studies from such cells confirmed cAMP enhancement of beta 3AR mRNA transcription. In these cells, beta 3AR mRNA increased in response to exposure to the beta 3AR agonist isoproterenol and remained elevated during exposures of up to 24-30 hr. During prolonged exposure to agonist, no downregulation of beta 3AR expression in 3T3-F442A cells occurred. Indeed, beta 3AR expression increased during agonist exposure to approximately 165% of basal expression. In marked contrast, beta 1AR expression declined by approximately 70% in response to chronic agonist exposure. These studies reveal a subtype-specific prolonged transcriptional regulation of a beta AR gene by the end product of its signal transduction pathway. Thus, the beta 3AR undergoes a paradoxical increase in receptor expression during chronic agonist exposure.
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PMID:Long-term agonist exposure induces upregulation of beta 3-adrenergic receptor expression via multiple cAMP response elements. 137 4

The promoter regions of the three mammalian transforming growth factor-beta genes (TGF-beta s 1, 2, and 3) have been recently cloned and characterized. The sequences show little similarity, suggesting different mechanisms of transcriptional control of these genes. To study differences in transcriptional regulation of mammalian and avian TGF-beta, we have cloned and sequenced the 5'-flanking region of chicken TGF-beta 3. Characterization of this region showed a TATA box and cAMP-responsive element (CRE) and AP-2 binding site consensus sequences starting at 12 and 28 base pairs, respectively, upstream from the TATA box. Moreover, four additional AP-2-like sites, 10 binding sites for the transcription factor Sp1, as well as two AP-1-like sites were also identified. Except for 32 base pairs of identity centered around the TATA box and CRE site and four other relatively small regions of identity, the chicken TGF-beta 3 promoter was found to be structurally very different from the human TGF-beta 3 promoter. Promoter fragments were cloned into a chloramphenicol acetyltransferase reporter plasmid to study functional activity. Basal transcriptional activity of the promoter was regulated in quail fibrosarcoma QM7 cells and in human adenocarcinoma A375 cells by multiple upstream elements including the TATA, CRE, and AP-2 sites. As in the human TGF-beta 3 promoter, the CRE site showed activation by forskolin, an effect which could be shown by expression of TGF-beta 3 mRNA in cultured chicken and quail cells as well. Our results indicate a complex pattern of transcriptional regulation of the chicken TGF-beta 3 gene and suggest that differences in the regulation of expression of the genes for mammalian and avian TGF-beta 3 may result in part from the unique structure of their 5'-flanking regions.
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PMID:Identification and characterization of the chicken transforming growth factor-beta 3 promoter. 140 6

Carnitine palmitoyltransferase (CPT) regulates the flux of long-chain fatty acids into the mitochondria for subsequent beta-oxidation. A 485 bp segment of the promoter for the gene encoding the 68 kDa CPT was isolated from a rat lambda DASH genomic library using the polymerase chain reaction. The promoter contained a consensus binding sequence for CREB (cyclic AMP response element binding protein) at -153 to -166, and for C/EBP alpha (CCAAT/enhancer binding protein) at -115 to -128. DNAase I footprinting using proteins isolated from rat liver nuclei indicated the presence of several regions of nuclear protein binding, most notably at -95 to -130, at -273 to -295, and at a wide region encompassing -395 to -465. DNAase I footprinting studies with purified CREB and C/EBP alpha confirmed that protein binding to DNA occurred at the sites predicted by the consensus sequences. The segment containing 481 bp of 5' flanking sequence plus 181 bp of untranslated mRNA was ligated to the structural gene for chloramphenicol acetyltransferase (CAT). When this plasmid was transfected into Hep G2 cells, CAT activity was stimulated 7-fold by addition of 1 mM-8-bromo-cyclic AMP (8-Br-cAMP) or co-transfection of the expression vector coding for the catalytic subunit of protein kinase A (PKA). The ability of several known second messengers and transcription factors to stimulate transcription of 68 kDa CPT promoter-CAT reporter was tested in co-transfection experiments. 68 kDa CPT promoter-CAT reporter transcription activity was stimulated 7-fold by addition of 8-Br-cAMP, and this induction was depressed 50% by the addition of phorbol esters. When the 68 kDa CPT promoter-CAT reporter was co-transfected with an expression vector for CREB or C/EBP alpha, transcription was increased 3- and 10-fold respectively. 8-Br-cAMP caused an additional 8-fold induction in the presence of each factor to yield 25- and 80-fold induction respectively. Co-transfection of the expression vector for c-jun also increased the CAT activity driven by the 68 kDa CPT promoter, while co-transfection with the expression vector for c-fos had no effect. When expression vectors for both c-jun and c-fos were co-transfected with the 68 kDa CPT promoter, c-fos depressed the induction seen with c-jun alone.
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PMID:Isolation and characterization of the promoter for the gene coding for the 68 kDa carnitine palmitoyltransferase from the rat. 825 Aug 54

The regulation of human corticotropin-releasing hormone (hCRH) gene promoter activity by inducers of cAMP was investigated by transient transfection with a construct containing the hCRH gene promoter fused to the chloramphenicol acetyltransferase gene. Expression of hCRH-chloramphenicol acetyltransferase was strongly enhanced by forskolin in the neuroblastoma SK-N-MC and choriocarcinoma JAR cell lines. Overexpression of the catalytic subunit of protein kinase A dispensed the need for forskolin, and cotransfection of cAMP-responsive element-binding protein cDNAs enhanced forskolin-dependent expression of the hCRH promoter. Progressive 5'-end deletions of the hCRH promoter delineated a cAMP- responsive region between -226 and -164 base pairs. This fragment contained the sequence TGACGTCA at -221 base pairs, consistent with the consensus motif for a CRE. A homologous oligonucleotide responded to cAMP when cloned in either orientation in front of the thymidine kinase promoter. However, the level of constitutive and inductive cAMP expression was dependent on the cell line and on intrinsic properties of the promoter. Mutation of the wild type CRH-CRE sequence into an AP-1 site (TGAGTCA) completely abolished stimulation by cAMP. In contrast, coexpression of the catalytic subunit of protein kinase A dispensed the need for stimulation with forskolin, which showed that the CRH-CRE oligonucleotide served as a functional equivalent of the native CRE element.
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PMID:Identification and characterization of a 3',5'-cyclic adenosine monophosphate-responsive element in the human corticotropin-releasing hormone gene promoter. 148 Jan 79

To study how the expression of the D1A dopamine receptor gene is regulated, a human genomic clone was isolated by using a rat cDNA as probe. A 2.3-kilobase genomic fragment spanning -2571 through -236 relative to the adenosine of the first methionine codon was sequenced. The gene has an intron of 116 base pairs in the 5' noncoding region, nucleotides -599 through -484 as determined by S1 mapping and reverse transcription-PCR. It has multiple transcription initiation sites located between -1061 and -1040. The promoter region lacks a TATA box and a CAAT box, is rich in G+C content, and has multiple putative binding sites for transcription factor Sp1. Thus, the promoter region of the human D1A gene has features of "housekeeping" genes. However, it also has consensus sequences for AP1 and AP2 binding sites and a putative cAMP response element. The ability of four deletion mutants of the 2.3-kilobase fragment to modulate transcription of the heterologous chloramphenicol acetyltransferase gene in the promoterless plasmid pCAT-Basic was determined. All mutants demonstrated substantial transcriptional activity in the murine neuroblastoma cell line NS20Y, which expresses the D1A gene endogenously. Transient expression assays suggested the presence of a positive modulator between nucleotides -1340 and -1102, and a negative modulator between -1730 and -1341. The four genomic fragments had no or very low transcriptional activity in NB41A3, C6, and Hep G2 cells, which are not known to express this gene. Thus, the human D1A gene belongs to the category of tissue-specific, regulated genes that have housekeeping-type promoters.
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PMID:Characterization of the 5' flanking region of the human D1A dopamine receptor gene. 155 11

It has been known that one of the signal transduction mechanisms in Escherichia coli is mediated by cAMP which binds to the receptor protein (CAP), and that CAP complexed with cAMP facilitates gene expression by binding to the specific sequences. To identify a molecular mechanism in eukaryotes similar to a cAMP-mediated pathway in E. coli, the function of the CAP binding site of lac gene in E. coli and the protein(s) interacting with it were examined in a mammalian system. From transient expression studies of the fusion gene between the chloramphenicol acetyltransferase and lac genes, it was found that the lacCAP binding site could act as an enhancer activity on the SV40 promoter, and also as an additive enhancer activity to the SV40 enhancer in HeLa cells. However, the activity was not stimulated by cpt-cAMP (a highly stable analogue of cAMP) in HeLa cells, although it was induced in PC12 cells. These results suggest that a bacterial cAMP responsive element may function also in eukaryotes as a cis-acting element in a cell type dependent manner. Results from gel mobility shift assays showed that a protein(s) exists that specifically binds to the lacCAP binding site in eukaryotic nuclear extracts. As one of the proteins binding to the above site, we have identified a 130 kDa protein by using the Southwestern method. Although a function of the 130 kDa protein has not yet been understood, there is a possibility that the 130 kDa protein may play a role in the regulation of cAMP-dependent gene expression.
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PMID:A eukaryotic nuclear protein of 130 kDa binds to a bacterial cAMP responsive element. 164 12

We have cloned a genomic fragment containing the promoter region of the rat protein phosphatase 2A alpha gene (PP-2A alpha). A 1.6 kb fragment of the 5' flanking region was sequenced. Three major transcriptional initiation sites were identified by the primer extension method using rat liver mRNA and found to be located 225, 222 and 220 bases upstream of the translational initiation site, respectively. Bacterial chloramphenicol acetyltransferase (CAT) assay revealed that a 503 bp SmaI fragment containing the transcriptional initiation sites had promoter activity, which was stronger than that of the SV40 early promoter on the pSV2CAT plasmid when introduced into NIH3T3 cells. Deletion of a 119 bp SacII fragment decreased its promoter activity considerably. The promoter region has an extremely high GC content and does not contain either a 'TATA box' or a 'CAAT box' suggesting that this promoter can be classified as that of a 'house keeping' gene, although there is only one typical GC-box (GGGCGG) immediately preceding the transcriptional initiation sites. There is a 10 base pair palindrome, 5'-GTGACGTCAC-3', 26 base pairs upstream of the +1 transcriptional initiation site, which is highly conserved in many other genes, whose expression is regulated by cAMP. The promoter activity was shown to be increased by forskolin treatment (10 microM) in NIH3T3 cells.
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PMID:Identification of the promoter region of the rat protein phosphatase 2A alpha gene. 165 Feb 51

To evaluate the function of the murine ornithine decarboxylase (ODC) gene promoter, expression of chimeric ODC-chloramphenicol acetyltransferase (CAT) plasmids (pODCcat) containing 1,658 nt of the ODC promoter sequence and its various 5'-deletions was analyzed. In transient expression assays with NIH/3T3 mouse cells, pODCcat constructs exhibited fairly strong promoter activity yielding CAT values up to 40% of those obtained with the viral promoter RSV. Interestingly, 5'-deletions of the pODCcat constructs increased the promoter activity over that achieved using the entire 1.6-kb 5'-flanking region, with the highest activity being observed with about 750 nt of the ODC promoter. This finding suggests that the distal part of the promoter includes DNA elements which are involved in repressing its function. The promoter region could be deleted down to the proximal 97 nt and still be stimulated by cAMP to the same extent as the 1.6-kb promoter. DNase I footprinting and methylation interference studies showed that a specific protein binds to the region from -59 to -39, which encompasses a DNA motif resembling the consensus cyclic AMP response element (CRE). However, comparative gel retardation and Southwestern blotting experiments with the putative ODC-CRE and the somatostatin promoter CRE indicated that the 70-kDa protein interacting with the CRE-like element of the ODC promoter is different from the well-characterized nuclear CRE-binding protein CREB.
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PMID:Protein-DNA interactions in the cAMP responsive promoter region of the murine ornithine decarboxylase gene. 165 Apr 55


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