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Query: EC:1.14.14.3 (luciferase)
 38,195 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To examine the relationship between the cardiac and skeletal muscle gene programs, the current study employs the regulatory (phosphorylatable) myosin light chain (MLC-2) as a model system. Northern blotting, primer extension, and RNase protection studies documented the high level expression of the cardiac MLC-2 mRNA in both mouse cardiac and slow skeletal muscle (soleus). Transgenic mouse lines harboring a 2100- or a 250-base pair rat cardiac MLC-2 promoter/luciferase fusion gene were generated, demonstrating high levels of luciferase activity in cardiac muscle, and only background luminescence in slow skeletal muscle and non-muscle tissues. As assessed by in situ hybridization, immunofluorescence, and luminescence assays of luciferase reporter activity in various regions of the heart, both the endogenous MLC-2 gene and the MLC-2 luciferase fusion gene were expressed exclusively in the ventricular compartment, with expression in the atrium at background levels. Point mutations within the conserved regulatory sites HF-1a and HF-1b significantly cripple ventricular muscle specificity, while mutation of the single E-box site was without effect, suggesting that ventricular muscle-specific expression occurs through an E-box-independent pathway. This study provides direct evidence that the cis regulatory sequences in the cardiac/slow twitch MLC-2 gene which confer cardiac and skeletal muscle-specific expression can be clearly segregated, suggesting that distinct regulatory programs may have evolved to control the tissue-specific expression of this single contractile protein gene in cardiac and skeletal muscle.
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PMID:Myosin light chain-2 luciferase transgenic mice reveal distinct regulatory programs for cardiac and skeletal muscle-specific expression of a single contractile protein gene. 137 40

The expression of the beta isoenzyme for protein kinase C is regulated developmentally and in response to inducers of cell differentiation (such as phorbol esters and 1 alpha,25-dihydroxyvitamin D3). The 5' segment of the gene for protein kinase C beta was cloned from a human leukocyte genomic library in EMBL3 bacteriophage. This segment of the gene (greater than 54 kilobases in length) encompassed the coding sequence for the amino-terminal regulatory domain of the enzyme, the 5'-untranslated region, and the 5'-flanking region. Initiation of transcription was identified by S1 nuclease analysis and confirmed by RNase protection analysis at 197 base pairs 5' of the initiator ATG. Sequence analysis of the 5'-flanking region revealed it to be extremely G+C-rich (> 80%) with many features of a CpG island. Comparison of sequence with known cis-regulatory motifs disclosed a number of potential regulatory elements including an octamer binding motif at -76, Sp1-binding sites at -94 and -63, E boxes at -110, -26, and +18, an AP-1 site at -442, and an AP-2 site at -330. To demonstrate promoter activity, a 630-base pair fragment extending from -587 to +43 was subcloned in front of a promoterless luciferase gene. This fragment was able to drive the expression of luciferase in transient transfections of human hematopoietic cells. Deletion analysis demonstrated that a fragment -111 to +43 was necessary and sufficient for promoter activity; this fragment did not contain TATA or CAAT motifs. The promoter was stimulated 8-20-fold by phorbol esters accounting for the previously observed transcriptional activation of protein kinase C beta. This phorbol ester responsiveness was conferred by the basal promoter (-111 to +43) and was independent of the AP-1 site. These results define a novel mechanism of protein kinase C autoregulation at a transcriptional level.
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PMID:Cloning and characterization of the major promoter of the human protein kinase C beta gene. Regulation by phorbol esters. 140 Mar 96

Rat IGF-I mRNAs contain one of two alternative 5'-untranslated regions which are encoded by alternative exons (exons 1 and 2) and whose expression is controlled by alternative promoter elements. We investigated the ability of fragments of DNA which contain exon 1 and its 5'-flanking region to regulate transcription of a luciferase reporter gene in transient transfection assays. Maximal promoter activity was obtained with a construct which contained 412 bp of 5'-flanking region, while constructs which contained 1120 and 1690 bp of 5'-flanking region induced approximately 50% less enzymatic activity. Mapping of transcription start sites by RNase protection assay demonstrated that native start sites were used by these constructs, although the relative use of different start sites was different from start site usage by the endogenous gene. These data demonstrate that the 5'-flanking region of exon 1 is capable of regulating transcription of IGF-I mRNAs.
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PMID:Characterization of a rat insulin-like growth factor I gene promoter. 147 69

Transient transfection is a widely used tool for the identification of cis-acting regulatory elements. These elements are detected by their effect on the expression of a reporter gene, which is quantified by measuring the reporter gene product in the form of mRNA, protein (hGH), or enzymes (CAT, luciferase). Measurements of mRNA levels have several advantages over enzyme or protein assays. However, mRNA quantification by RNase protection or S1 mapping has considerably lower signal-to-background ratio than protein assays and is therefore less sensitive. In this paper we report the development of a system that takes advantage of the polymerase chain reaction (PCR) to quantify rabbit beta-globin reporter gene expression. Cells are co-transfected with constructs whose activity is to be tested and a reference plasmid with a small deletion in the second exon of the beta-globin gene. We show that the ratio of the two amplified cDNA signals is a highly reliable measure of test gene expression. The sensitivity of this assay is at least 1000-fold higher than RNase protection.
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PMID:A PCR-based assay for reporter gene expression. 147 39

Investigations of the structure and expression of the N-ras gene in mammals has led to the identification of another gene designated unr, which is located immediately upstream of N-ras. These two genes are transcribed in the same orientation and the intergenic distance is of the order of 150 nucleotides. This genetic organization has been observed in the genome of guinea pig, rat, mouse and man with a very high level of sequence conservation in the intergenic region. This unusual gene clustering suggests that the transcriptional regulation of this locus could involve common regulatory sequences as well as transcriptional interference between the two genes. In this study, we have isolated and characterized the human unr promoter. A cluster of transcription initiation sites was mapped by primer extension and RNase protection and shown to be located in a CpG island devoid of TATA and CAAT boxes. Functional organization of the promoter was investigated by measuring the ability of a set of 5' deletions within a1 kb promoter region to drive the expression of the luciferase gene. These studies indicated a very strong promoter activity in NIH 3T3 cells and the presence of positive and negative regulatory domains. Nevertheless, a 90 bp fragment showed the same level of promoter activity as the 1 kb fragment. We also showed that ras genes can transactivate the unr promoter activity and that the 90 bp fragment responded to this transactivation.
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PMID:Organization of the unr/N-ras locus: characterization of the promoter region of the human unr gene. 147 96

We sought to determine the cis-acting elements responsible for the pattern of tissue specific expression of the mouse alpha 2(I) collagen gene. Using an RNase protection assay we first verified that expression of the alpha 2(I) collagen gene is mainly confined to tendons, bone, and skin in mice. Both transgenic mice and DNA transfection of tissue culture cells were used as experimental approaches. Transgenic mice lines were generated harboring chloramphenicol acetyltransferase (CAT) chimeric genes that contained either (a) 2000 base pairs (bp) of 5'-flanking sequences of the mouse alpha 2(I) collagen gene plus additional sequences between +418 and +1524 of the first intron of this gene or (b) the same promoter sequences without intron sequences or (c) the 350-bp proximal promoter sequences. Transgenic mice containing both types of 2000-bp promoters showed a pattern of CAT expression that was tissue specific. The presence of sequences of the first intron in the transgene did not increase the level of promoter activity. Transgenic mice harboring the 350-bp alpha 2(I) collagen promoter also showed a pattern that was tissue-specific except that high level expression also occurred in the brain. This suggests that negative regulation is an important component of tissue-specific expression. In order to analyze the first 350 bases in detail, we performed transient expression experiments, using promoter fragments attached to the luciferase reporter gene. Fibroblasts, which show a high level expression of the endogenous alpha 2(I) collagen gene, and B cells, in which the gene is silent, were transfected with a series of deletions and substitution mutations within the proximal 350-bp promoter. These experiments were unable to define unique cell-specific cis-acting elements. However, when the sequence between -315 and -284 was tandemly repeated upstream of a minimal alpha 2(I) collagen promoter (-41 to +54), the activity of this construction was considerably higher in fibroblasts than in B cells when compared with the minimal promoter itself. In gel retardation assays, the levels of complexes that bind to this sequence were higher in fibroblast nuclear extracts than in myeloma nuclear extracts. Our results are consistent with the hypothesis that the -315 to -284 DNA sequence participates in the cell-specific control of the alpha 2(I) collagen gene in fibroblasts.
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PMID:Tissue-specific expression of the mouse alpha 2(I) collagen promoter. Studies in transgenic mice and in tissue culture cells. 152 81

A high molecular weight (HMW) fraction of the 150,000 g supernatant of rat brain homogenates contains protein-tRNA complexes which are able to incorporate [3H]Arg and [3H]Lys into tRNA. The aminoacylation of tRNA(Arg) was found to be dependent on ATP and inhibited by RNase. Conversely, the aminoacylation of tRNA(Lys) did not require exogenous ATP and was resistant to RNase and ATPase. In HMW fractions of regenerating rat sciatic nerves, the charging of both tRNA(Arg) and tRNA(Lys) was resistant to RNase and ATPase and did not require exogenous ATP. Because sciatic nerves are rich in axoplasm and tRNAs are known to be present in axons, we tested the hypothesis that degradative enzyme-resistant, ATP-tRNA complexes were of axonal origin. In HMW fractions from rat liver (containing no axons), both tRNA(Arg) and tRNA(Lys) were sensitive to RNase and required exogenous ATP for charging. But, in similar fractions of axoplasm obtained from the giant axon of squid, both tRNAs were insensitive to RNase and ATPase and did not require exogenous ATP for charging. These results suggest that tRNAs in axons are present in protected HMW complexes and contain endogenous stores of ATP. The presence of ATP in the HMW complexes was demonstrated by the luciferase-luciferin assay for ATP. The nature of the protection of tRNAs from RNases was examined by dissociating proteins from HMW complexes by boiling, treating with proteinase K, or overhomogenizing the tissue. These procedures failed to render brain tRNA(Lys) susceptible to RNase. But phenol-extracted, ethanol-precipitated brain tRNA(Lys) was sensitive to RNase, suggesting that the protection of tRNA(Lys) may be by a protease- and heat-resistant polypeptide or by a nonproteinaceous mechanism.
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PMID:Evidence that axonal tRNAs are resistant to RNase and ATPase and can be aminoacylated in the absence of exogenous ATP. 153 73

The molecular mechanisms that regulate intestine-specific gene expression and the transition from proliferating, undifferentiated crypt cells to nonproliferating, differentiated villus cells are unknown. Sucrase-isomaltase is an apical membrane disaccharidase that is found exclusively in enterocytes of adult intestine and is expressed in a complex pattern along the intestinal crypt-villus axis. To investigate the regulation of sucrase-isomaltase, we have cloned and sequenced 3.6 kilobases of the 5'-flanking region of the human sucrase-isomaltase gene. The transcriptional start site was mapped in human small intestine and in a colonic adenocarcinoma cell line (Caco-2) using an anchored polymerase chain reaction, primer extension, and RNase protection assays. The 5'-flanking DNA of the gene was linked to either chloramphenicol acetyltransferase or luciferase reporter genes and used for transfection into Caco-2, HeLa, and HepG2 cells. This analysis demonstrated that intestine-specific transcription of the sucrase-isomaltase gene involves both proximal and distal regulatory elements. Use of sucrase-isomaltase as a model gene will allow investigation of the mechanisms that regulate transcription of enterocyte-specific genes, developmental gene expression in the small intestine and colon, and the process of differentiation as epithelial cells migrate from intestinal crypts onto the villus in adult intestine.
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PMID:Isolation and characterization of the human sucrase-isomaltase gene and demonstration of intestine-specific transcriptional elements. 156 17

To study the mechanisms which mediate the transcriptional activation of cardiac genes during alpha adrenergic stimulation, the present study examined the regulated expression of three cardiac genes, a ventricular embryonic gene (atrial natriuretic factor, ANF), a constitutively expressed contractile protein gene (cardiac MLC-2), and a cardiac sodium channel gene. alpha 1-Adrenergic stimulation activates the expression and release of ANF from neonatal ventricular cells. As assessed by RNase protection analyses, treatment with alpha-adrenergic agonists increases the steady-state levels of ANF mRNA by greater than 15-fold. However, a rat cardiac sodium channel gene mRNA is not induced, indicating that alpha-adrenergic stimulation does not lead to an increase in the expression of all cardiac genes. Studies employing a series of rat ANF luciferase and rat MLC-2 luciferase fusion genes identify 315- and 92-base pair cis regulatory sequences within an embryonic gene (ANF) and a constitutively expressed contractile protein gene (MLC-2), respectively, which mediate alpha-adrenergic-inducible gene expression. Transfection of various ANF luciferase reporters into neonatal rat ventricular cells demonstrated that upstream sequences which mediate tissue-specific expression (-3003 to -638) can be segregated from those responsible for inducibility. The lack of inducibility of a cardiac Na+ channel gene, and the segregation of ANF gene sequences which mediate cardiac specific from those which mediate inducible expression, provides further insight into the relationship between muscle-specific and inducible expression during cardiac myocyte hypertrophy. Based on these results, a testable model is proposed for the induction of embryonic cardiac genes and constitutively expressed contractile protein genes and the noninducibility of a subset of cardiac genes during alpha-adrenergic stimulation of neonatal rat ventricular cells.
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PMID:Co-regulation of the atrial natriuretic factor and cardiac myosin light chain-2 genes during alpha-adrenergic stimulation of neonatal rat ventricular cells. Identification of cis sequences within an embryonic and a constitutive contractile protein gene which mediate inducible expression. 185 Apr 19

Maize transposable elements, when inserted in or near genes, alter expression by several transcriptional and post-transcriptional mechanisms. Three independent, unstable insertions of the transposable element Mutator (Mu) into the first intron of the Alcohol dehydrogenase-1 (Adh1) gene have been shown to decrease expression [Strommer et al. (1982). Nature 300, 542-544]. We have developed an approach to elucidate the underlying molecular mechanisms responsible for the mutant phenotypes. Mu1 elements were inserted into Adh1-S intron 1 in vitro to create plasmid facsimiles of the mutant alleles. The Mu1 element was also inserted at novel positions within intron 1 to create new mutations. The Mu1/intron constructions were placed between the Adh1-S promoter/exon 1 segment and a reporter gene (firefly luciferase or beta-glucuronidase), and these chimeric gene constructs were tested in transient assays in maize protoplasts. When compared with the appropriate control, the Mu1 insertions decreased reporter gene expression to levels approximating the alcohol dehydrogenase enzyme activities observed for the Adh1-S mutants in vivo. The Mu1 insertions also showed a polarity effect with luciferase expression increasing as the insertions were placed nearer the 3' splice junction. In addition, Mu1 insertions within a different intron, actin intron 3, also significantly reduced luciferase expression, indicating that Mu1 insertions within introns are likely to diminish expression in many genes. The presence of the Mu1 sequences was correlated with decreased levels of steady-state luciferase transcript. Deletion analysis of the Mu1 element and RNase mapping indicate that the transposable element contains RNA processing signals in its central region that are largely responsible for the decrease in expression.
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PMID:Insertion of Mu1 elements in the first intron of the Adh1-S gene of maize results in novel RNA processing events. 196 75


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