Preferential Transcription of Rabbit Aldh1a1 in the Cornea: Implication of Hypoxia-Related Pathways
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Here we examine the molecular basis for the known preferential expression of rabbit aldehyde dehydrogenase class 1 (ALDH1A1) in the cornea. The rabbit Aldh1a1 promoter-firefly luciferase reporter transgene (-3519 to +43) was expressed preferentially in corneal cells in transfection tests and in transgenic mice, with an expression pattern resembling that of rabbit Aldh1a1. The 5' flanking region of the rabbit Aldh1a1 gene resembled that in the human gene (60.2%) more closely than that in the mouse (46%) or rat (51.5%) genes. We detected three xenobiotic response elements (XREs) and one E-box consensus sequence in the rabbit Aldh1a1 upstream region; these elements are prevalent in other highly expressed corneal genes and can mediate stimulation by dioxin and repression by CoCl(2), which simulates hypoxia. The rabbit Aldh1a1 promoter was stimulated fourfold by dioxin in human hepatoma cells and repressed threefold by CoCl(2) treatment in rabbit corneal stromal and epithelial cells. Cotransfection, mutagenesis, and gel retardation experiments implicated the hypoxia-inducible factor 3alpha/aryl hydrocarbon nuclear translocator heterodimer for Aldh1a1 promoter activation via the XREs and stimulated by retinoic acid protein 13 for promoter repression via the E-box. These experiments suggest that XREs, E-boxes, and PAS domain/basic helix-loop-helix transcription factors (bHLH-PAS) contribute to preferential rabbit Aldh1a1 promoter activity in the cornea, implicating hypoxia-related pathways.Keywords:
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Chloramphenicol acetyltransferase
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Monitoring promoter response to environmental changes using reporter systems has provided invaluable information regarding cellular state. With the development of in vivo luciferase reporter systems, inexpensive, sensitive and accurate promoter assays have been developed without the variability reported between in vitro samplings. Current luciferase reporter systems, however, are largely inflexible to modifications to the promoter of interest. To overcome problems in flexibility and stability of these expression vectors, we report the creation of a novel vector system which introduces a cytosol-localized Photinus pyralis luciferase [LUC*(-SKL)] capable of one-step, in vivo measurements into a promoter-reporter system via PCR-based gene deletion and fusion. After introduction of the reporter under HUG1 promoter control, cytosolic localization was confirmed by fluorescence microscopy. The dose-response of this novel construct was then compared with that of a similar HUG1Δ::yEGFP1 promoter-reporter system and shown to give a similar response pattern.
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The effects of cyclic AMP (cAMP)-elevating agents on the activity of cis-acting gene promoter sequences are frequently studied using the luciferase-reporter-gene system. The aim of the present study was to assess whether cAMP-elevating agents induce any changes in the level of luciferase activity independently of a transcriptional activation of promoter elements. Chloramphenicol acteyltransferase (CAT) and luciferase reporter genes under the control of the same promoter elements were transiently expressed in primary cultures of human vascular smooth-muscle cells. Transfected cells were treated with a cell-permeable and non-hydrolysable cAMP analogue, 2'-O-monobutyryl-8-bromo cAMP, or with the cAMP-elevating agents forskolin and prostaglandin E1 (PGE1). Forskolin and PGE1 induced a significant increase in the level of luciferase activity, but had no effect on CAT activity. Conclusions based solely on the use of the luciferase-reporter-gene system in studies involving promoter activation by cAMP-elevating agents could therefore be misleading.
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Tretinoin
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Objective To construct luciferase reporter gene vectors containing B7-H1 promoter region and to detect promoter activity in Hep G2 cells. Methods Fragments of the B7-H1 gene 5'-UTR promoters were amplified by PCR and cloned into PGL3 basic vector and named as P88,P175,P203,P398,P723,and P960 respectively.Then Hep G2 cells,were transfected with these constructed plasmids. The expression of luciferase before and after the addition of IFN-γ was detected by dual-luciferase(LUC) reporter assay system kit. Results Five luciferase reporter gene vectors containing B7-H1 promoter region were successfully constructed. The recombinant constructs were transiently transfected into Hep G2 cells. After the addition of IFN-γ,LUC detection assay showed that the expression of LUC was significantly enhanced by P175,P203,P398,P723 or P960,but not by P88. Conclusions Luciferase reporter gene vectors containing B7-H1 promoter region were successfully constructed,which may be valuable for further study on B7-H1 promoter activity and molecular mechanism.
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Objective To explore the estrogenic effects and disruptive mechanism of NP and BPA by reporter gene-based assays we developed. Methods pERE-Luc plamid was generated by inserting estrogen response element (ERE) fragment into MCS of pGL3-promoter vector. MCF7 cells were cotransfected with pERE-Luc and phRL-SV40 using Sofast transfection reagent. The cells then treated with 17beta-estradiol (E2), tamoxifen (Tam), nonylphenol(NP) and bisphenol A (BPA) and expression of the repoter gene in the cell lysates was assayed using Dual-Lucferase reporter assay system. Results The pERE-Luc plasmid was constructed. Luciferase activities of MCF7 cells transfected pERE-Luc showed dose-responed realitionship with E2. 1 x 10(-11) mol/L E2 could induce the expression of reporter gene and 1 x 10(-9) mol/L E2 resulted in the largest luciferase activity. E2 couldn't induce the luciferase activity without pERE-Luc. Tam is a complete antagonist, inhibited the E2-induced luciferase expression. NP induced the luciferase activity at concertrations > 1 x 10(-6) mol/L, BPA induced the luciferase activity at concertrations > 1 x 10(-6) mol/L. The estrogenic activity of NP was more than BPA. Conclusion The assay we established is usful, NP and BPA showed estrogenic activities.
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Reporter gene systems based upon modified luciferase genes isolated from organisms, ranging from bacteria to insects, have proven to be important tools for plant molecular studies. The biochemical characteristics of these genes combine very high sensitivity with the ability to determine reporter activity non-destructively in vivo, allowing many applications in plants that cannot be accomplished using any other single reporter system. The relative ease of in situ detection of the firefly luciferase has made it an especially successful reporter for screening mutants in the model plant genetic system, Arabidopsis thaliana. The rapid turnover rate of luciferase has aided the characterization of promoters and elements that are influenced by time-sensitive factors such as circardian rhythm (diurunal cycles), gene silencing, and environmental stresses. The high sensitivity of luciferase as a reporter has facilitated the analysis and development of synthetic promoters for plant gene expression. Additionally, the biochemical characteristics of different luciferases have allowed their use as in situ indicators of metabolic activity and oxygen levels, as well as direct indicators of in vivo protein-protein interaction. The various applications of luciferase-based reporter systems in plants will be the subject of this review.
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Abstract Reporter gene assays are widely used to study cellular signaling and transcriptional activity. Few studies describe the use of reporter genes for studying cellular responses on complex body fluids, such as urine and blood. Selection of the optimal reporter gene is crucial for study outcome. Here, we compared the characteristics of five reporter genes (Firefly luciferase, stable- and unstable Nano luciferase, secretable Gaussia luciferase and Red Fluorescent Protein) to study complex body fluids. For this comparison, the NFκB Response Element (NFκB-RE) and Smad Binding Element (SBE) were identically cloned into the five different reporter vectors. Reporter characteristics were evaluated by kinetic and concentration–response measurements in SW1353 and HeLa cell lines. Finally, reporter compatibility with complex body fluids (fetal calf serum, knee joint synovial fluid and human serum) and inter-donor variation were evaluated. Red Fluorescent Protein demonstrated poor inducibility as a reporter gene and slow kinetics compared to luciferases. Intracellularly measured luciferases, such as Firefly luciferase and Nano luciferase, revealed good compatibility with complex body fluids. Secreted Gaussia luciferase appeared to be incompatible with complex body fluids, due to variability in inter-donor signal interference. Unstable Nano luciferase demonstrated clear inducibility, high sensitivity and compatibility with complex body fluids and therefore can be recommended for cellular signaling studies using complex body fluids.
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In an earlier gene expression study, the authors identified a novel antimicrobial gene, Peptidoglycan recognition protein 1 (Pglyrp1), in the mouse cornea. Here the expression of the Pglyrp1 transcript and the encoded protein, PGLYRP1, in the cornea was investigated. The role of PGLYRP1 in the cornea was further investigated using wild-type and Pglyrp1-deficient mice. This is the first report of this antimicrobial protein in the cornea.PGLYRP1 was detected in the cornea and was further localized to the epithelium by immunohistology, confocal microscopy, immunoblotting, and real-time PCR. The role of PGLYRP1 in the cornea was investigated by comparing the response of wild-type and Pglyrp1(-/-) mice to corneal epithelial wounds and Pseudomonas aeruginosa-mediated corneal infections. The antibacterial effects of corneal PGLYRP1 were assayed by measuring bacterial growth in vitro, in the presence of wild-type corneal epithelial extracts, before and after antibody-mediated blocking of PGLYRP1.PGLYRP1 is expressed at high levels in the mouse corneal epithelium. PGLYRP1 was localized to the mouse corneal epithelium and the human corneal epithelium. The Pglyrp1(-/-) mouse shows delayed healing and poor clearing of bacterial keratitis; in vitro its epithelial protein extract shows reduced bacteriostatic activity compared with wild-type mice.PGLYRP1 is a novel antimicrobial protein of the corneal epithelium and protects the ocular surface from bacterial infections.
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