Synthesis of active firefly luciferase by in vitro translation of RNA obtained from adult lanterns

Optimization of Constitutive Promoters Using a Promoter-Trapping Vector in Burkholderia pyrrocinia JK-SH007

Selecting suitable promoters to drive gene overexpression can provide significant insight into the development of engineered bacteria. In this study, we analyzed the transcriptome data of Burkholderia pyrrocinia JK-SH007 and identified 54 highly expressed genes. The promoter sequences were located using genome-wide data and scored using the prokaryotic promoter prediction software BPROM to further screen out 18 promoter sequences. We also developed a promoter trap system based on two reporter proteins adapted for promoter optimization in B. pyrrocinia JK-SH007: firefly luciferase encoded by the luciferase gene set (Luc) and trimethoprim (TP)-resistant dihydrofolate reductase (TP^r). Ultimately, eight constitutive promoters were successfully inserted into the probe vector and transformed into B. pyrrocinia JK-SH007. The transformants were successfully grown on Tp antibiotic plates, and firefly luciferase expression was determined by measuring the relative light unit (RLU). Five of the promoters (P4, P9, P10, P14, and P19) showed 1.01-2.51-fold higher activity than the control promoter λ phage transcriptional promoter (PRPL). The promoter activity was further validated via qPCR analysis, indicating that promoters P14 and P19 showed stable high transcription levels at all time points. Then, GFP and RFP proteins were overexpressed in JK-SH007. In addition, promoters P14 and P19 were successfully used to drive gene expression in Burkholderia multivorans WS-FJ9 and Escherichia coli S17-1. The two constitutive promoters can be used not only in B. pyrrocinia JK-SH007 itself to gene overexpression but also to expand the scope of application.

Firefly genomes illuminate the evolution of beetle bioluminescent systems

Fireflies are one of the best-known bioluminescent organisms, and the reaction mechanism and ecological utility of bioluminescence have been well-studied. Genome assemblies of six species of bioluminescent beetles have recently been published. These studies have focused on the evolution of novelties; luciferase, and the biosynthesis of luciferin and defensive chemicals. For example, clustering of the luciferase gene with acyl-CoA synthetase genes on a chromosome in luminous beetle genomes suggests the involvement of tandem gene duplications and neofunctionalization during the evolution of beetle bioluminescence. Several candidate genes for critical roles in beetle bioluminescence have been identified, but their functional analyses are still ongoing. The establishment of a long-term mass-rearing system and strain will be the key for the post-genome research on bioluminescent beetles. Lastly, the application of contemporary chromosome-scale genome assembly techniques to luminous beetles will help resolve outstanding evolutionary questions, such as how many times bioluminescence evolved in this clade.

Suppression of Urokinase-Type Plasminogen Activator Receptor by Docosahexaenoic Acid Mediated by Heme Oxygenase-1 in 12-O-Tetradecanoylphorbol-13-Acetate-Induced Human Endothelial Cells

Urokinase-type plasminogen activator receptor (uPAR) plays a crucial role in inflammation and tumor metastasis. Docosahexaenoic acid (DHA), a representative omega-3 polyunsaturated fatty acid, has been shown to exhibit anti-inflammatory and anti-tumor properties. However, the mechanism by which DHA negatively regulates uPAR expression is not yet understood. The aim of this study was to investigate the effect of DHA on 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced uPAR expression and potential role of heme oxygenase-1 (HO-1) in DHA-induced inhibition of uPAR in human endothelial ECV304 cells. Results showed that TPA induced uPAR expression in a time dependent manner, while DHA inhibited uPAR expression in a concentration-dependent manner. Moreover, treatment with DHA induced HO-1 expression in a time- and concentration-dependent manner. In addition, DHA-induced inhibition of uPAR expression and cell invasion in TPA-stimulated cells was reversed by si-HO-1 RNA. Induction of HO-1 by ferric protoporphyrin IX (FePP) inhibited TPA-induced uPAR expression, and this effect was abolished by treatment with the HO-1 inhibitor tin protoporphyrin IX (SnPP). Additionally, carbon monoxide, an HO-1 product, attenuated TPA-induced uPAR expression and cell invasion. Collectively, these data suggest a novel role of DHA-induced HO-1 in reducing uPAR expression and cell invasion in human endothelial ECV304 cells.

Illuminating the Regenerative Properties of Stem Cells In Vivo with Bioluminescence Imaging

Preclinical animal studies are essential to the development of safe and effective stem cell therapies. Bioluminescence imaging (BLI) is a powerful tool in animal studies that enables the real-time longitudinal monitoring of stem cells in vivo to elucidate their regenerative properties. This review describes the application of BLI in preclinical stem cell research to address critical challenges in producing successful stem cell therapeutics. These challenges include stem cell survival, proliferation, homing, stress response, and differentiation. The applications presented here utilize bioluminescence to investigate a variety of stem and progenitor cells in several different in vivo models of disease and implantation. An overview of luciferase reporters is provided, along with the advantages and disadvantages of BLI. Additionally, BLI is compared to other preclinical imaging modalities and potential future applications of this technology are discussed in emerging areas of stem cell research.

Firefly genomes illuminate parallel origins of bioluminescence in beetles

Fireflies and their luminous courtships have inspired centuries of scientific study. Today firefly luciferase is widely used in biotechnology, but the evolutionary origin of bioluminescence within beetles remains unclear. To shed light on this long-standing question, we sequenced the genomes of two firefly species that diverged over 100 million-years-ago: the North American Photinus pyralis and Japanese Aquatica lateralis. To compare bioluminescent origins, we also sequenced the genome of a related click beetle, the Caribbean Ignelater luminosus, with bioluminescent biochemistry near-identical to fireflies, but anatomically unique light organs, suggesting the intriguing hypothesis of parallel gains of bioluminescence. Our analyses support independent gains of bioluminescence in fireflies and click beetles, and provide new insights into the genes, chemical defenses, and symbionts that evolved alongside their luminous lifestyle.

Generating a Battery of Monoclonal Antibodies Against Firefly Luciferase for Dot Blot Analysis, Western Blot Analysis, and Immunostaining of Cells in Culture and Paraffin Sections

Firefly luciferase (FLuc) is commonly used as a reporter gene PpyLuc1 in bioanalytical assays. We have produced five mouse-derived monoclonal antibodies (mAbs) that recognize FLuc. The mAbs, DSHB-LUC-2, DSHB-LUC-3, DSHB-LUC-9, DSHB-LUC-16, and DSHB-LUC-24, were generated by immunizing mice with purified 6xHIS-tagged FLuc (6xHis-FLuc) in suspension with an adjuvant. All five were validated by dot blots. Four of the mAbs provided strong signals in western blot analysis, and one a weak signal. All five were validated for immunostaining in fixed cell culture. Only one stained cells embedded in paraffin. The five mAbs are available at cost through the Developmental Studies Hybridoma Bank (DSHB), a nonprofit National Resource created by the National Institutes of Health.

Biochemical characteristics and gene expression profiles of two paralogous luciferases from the Japanese firefly Pyrocoelia atripennis (Coleoptera, Lampyridae, Lampyrinae): insight into the evolution of firefly luciferase genes

The same green luminescence is generated by two luciferase isoforms: PatLuc1 is used in lanterns of various stages, and PatLuc2 is used in the body of immobile/less-mobile stages.

Luciferase Reporter Assays to Study Transcriptional Activity of Hedgehog Signaling in Normal and Cancer Cells

The measurement of the transcriptional activity of the HH signaling pathway is widely used as an indication of pathway activation. Luciferase reporter assays are powerful tools to measure the specific ability of a transcription factor to bind to its consensus sequence and to activate transcription of target genes. Here, we describe a protocol to measure the transcriptional activity of the HH pathway in normal and cancer cells. This technique allows studying the activity of GLI transcription factors and their modulation by drugs and/or other factors.

Luciferase reporter assay in Drosophila and mammalian tissue culture cells

Luciferase reporter gene assays are one of the most common methods for monitoring gene activity. Because of their sensitivity, dynamic range, and lack of endogenous activity, luciferase assays have been particularly useful for functional genomics in cell-based assays, such as RNAi screening. This unit describes delivery of two luciferase reporters with other nucleic acids (siRNA/dsRNA), measurement of the dual luciferase activities, and analysis of data generated. The systematic query of gene function (RNAi) combined with the advances in luminescent technology have made it possible to design powerful whole genome screens to address diverse and significant biological questions.

Mutant firefly luciferases with improved specific activity and dATP discrimination constructed by yeast cell surface engineering

Pyrosequencing system utilizing luciferase is one of the next-generation DNA sequencing systems. However, there is a crucial problem with the current pyrosequencing system: luciferase cannot discriminate between ATP and dATP completely, and dATPαS must be used as the dATP analogue. dATPαS is expensive and has low activity for the enzyme. If luciferase can clearly recognize the difference between ATP and dATP, dATP could be used instead of the expensive dATPαS in the pyrosequencing system. We attempted to prepare a novel luciferase with improved specific activity and dATP discrimination with the molecular display method. First, we selected two amino acid residues, Ser440 and Ser456, as target residues for mutation from the whole sequence of Photinus pyralis luciferase; we comprehensively mutated these two amino acids. A mutant luciferase library was constructed using yeast cell surface engineering. Through three step-wide screenings with individual conditions, we easily and speedily isolated three candidate mutants from 1,152 candidates and analyzed the properties of these mutants. Consequently, we succeeded in obtaining interesting mutant luciferases with improved specific activity and dATP discrimination more conveniently than with other methods.

Glucocorticoids increase VE-cadherin expression and cause cytoskeletal rearrangements in murine brain endothelial cEND cells

Recent studies have shown the influence of glucocorticoids on the expression of the tight junction protein occludin in the brain capillary endothelial cell line cEND, contributing to improvement in endothelial barrier functions. In this study, we investigated glucocorticoid effects on the expression of the adherens junction proteins VE- (vascular-endothelial) cadherin, alpha-catenin and beta-catenin as well as that of ZO-1, the plaque protein shared by both adherens and tight junctions on stimulation with dexamethasone. We were able to show a positive influence of dexamethasone administration on VE-cadherin protein levels as well as a rearrangement of VE-cadherin protein to the cytoskeleton after dexamethasone treatment. Investigation of transcriptional activation of the VE-cadherin promoter by dexamethasone, however, did not point to direct glucocorticoid-mediated VE-cadherin gene induction but rather suggested indirect steroid effects leading to increased VE-cadherin protein synthesis. Dexamethasone was further shown to induce cellular differentiation into a cobblestone cellular morphology and reinforcement of adherens junctions concomitant with the increased anchorage of VE-cadherin to the actin cytoskeleton. We thus propose that glucocorticoid effects on VE-cadherin protein synthesis and organization are important for the formation of both adherens and tight junction, and for improved barrier properties in microvascular brain endothelial cells.

Firefly luminescence: a historical perspective and recent developments

Significant advances have occurred regarding our knowledge of firefly luciferase mechanisms. Although most of this progress was an outcome of molecular biology and structural studies, important achievements have also occurred on its fundamental chemistry. Those developments are here summarized and presented in a historical perspective.

Rapid and direct quantitative RT-PCR method to measure promoter activity

This Note describes a novel rapid and direct quantitative method for examining the activity of genetic response elements. This method will provide an alternative to the classically used "reporter gene" activity assays. We show that a transfected genetic cis-regulatory element that responds to the transcription factor p53 gives a quantitative read-out at the RNA level that parallels that of an endogenous p53 responsive gene, p21 waf1/cip1. The correlation between the endogenous p21 gene expression in response to p53 and the transfected cis element is remarkable. This method is more direct and potentially faster than traditional promoter-reporter assays.

Inhibition of firefly luciferase by alkane analogues

We reported that anesthetics increased the partial molal volume of firefly luciferase (FFL), while long-chain fatty acids (LCFA) decreased it. The present study measured the actions of dodecanol (neutral), dodecanoic acid (negatively charged), and dodecylamine (positively charged) hydrophobic molecules on FFL. The interaction modes are measured by (1) ATP-induced bioluminescence of FFL and (2) fluorescence of 2-(p-toluidino)naphthalene-6-sulfonate (TNS). TNS fluoresces brightly in hydrophobic media. It competes with the substrate luciferin on the FFL binding. From the Scatchard plot of TNS titration, the maximum binding number of TNS was 0.83, and its binding constant was 8.27 x 10(5) M(-1). Job's plot also showed that the binding number is 0.89. From the TNS titration of FFL, the binding constant was estimated to be 8.8 x 10(5) M(-1). Dodecanoic acid quenched the TNS fluorescence entirely. Dodecanol quenched about 25% of the fluorescence, whereas dodecylamine increased it. By comparing the fluorescence of TNS and bioluminescence of FFL, the binding modes and the inhibition mechanisms of these dodecane analogues are classified in three different modes: competitive (dodecanoic acid), noncompetitive (dodecylamine), and mixed (dodecanol).

A possible approach to site-specific insertion of two different unnatural amino acids into proteins in mammalian cells via nonsense suppression

The site-specific insertion of an unnatural amino acid into proteins in vivo via nonsense suppression has resulted in major advances in recent years. The ability to incorporate two different unnatural amino acids in vivo would greatly increase the scope and impact of unnatural amino acid mutagenesis. Here, we show the concomitant suppression of an amber and an ochre codon in a single mRNA in mammalian cells by importing a mixture of aminoacylated amber and ochre suppressor tRNAs. This result provides a possible approach to site-specific insertion of two different unnatural amino acids into any protein of interest in mammalian cells. To our knowledge, this result also represents the only demonstration of concomitant suppression of two different termination codons in a single gene in vivo.

pH-dependent entry of severe acute respiratory syndrome coronavirus is mediated by the spike glycoprotein and enhanced by dendritic cell transfer through DC-SIGN

The severe acute respiratory syndrome coronavirus (SARS-CoV) synthesizes several putative viral envelope proteins, including the spike (S), membrane (M), and small envelope (E) glycoproteins. Although these proteins likely are essential for viral replication, their specific roles in SARS-CoV entry have not been defined. In this report, we show that the SARS-CoV S glycoprotein mediates viral entry through pH-dependent endocytosis. Further, we define its cellular tropism and demonstrate that virus transmission occurs through cell-mediated transfer by dendritic cells. The S glycoprotein was used successfully to pseudotype replication-defective retroviral and lentiviral vectors that readily infected Vero cells as well as primary pulmonary and renal epithelial cells from human, nonhuman primate, and, to a lesser extent, feline species. The tropism of this reporter virus was similar to that of wild-type, replication-competent SARS-CoV, and binding of purified S to susceptible target cells was demonstrated by flow cytometry. Although myeloid dendritic cells were able to interact with S and to bind virus, these cells could not be infected by SARS-CoV. However, these cells were able to transfer the virus to susceptible target cells through a synapse-like structure. Both cell-mediated infection and direct infection were inhibited by anti-S antisera, indicating that strategies directed toward this gene product are likely to confer a therapeutic benefit for antiviral drugs or the development of a SARS vaccine.

YB-1 is upregulated during prostate cancer tumor progression and increases P-glycoprotein activity

BACKGROUND

Currently, the main obstacle to curing advanced prostate cancer is development of androgen independence (AI), where malignant cells acquire the ability to survive in the absence of androgens. Our initial experimental approach used cDNA microarrays to characterize changes in gene expression in the LNCaP human prostate tumor model during progression to AI. The transcription factor Y-box binding protein (YB-1) was shown to be one of the genes upregulated. We focused on increased YB-1 expression during progression in clinical specimens, and further examined one of its downstream targets, P-glycoprotein (P-gp).

METHODS

Northern blot analysis was performed on LNCaP tumor series, as well as immunohistochemical analyses of human prostate cancer tissue samples. YB-1 was transiently transfected and transport analysis were performed to analyze P-gp efflux activity.

RESULTS

YB-1 expression is markedly increased during benign to malignant transformation and further following androgen ablation. In addition, increased YB-1 expression after castration in the LNCaP model is linked to upregulation of P-gp. We demonstrate that YB-1 upregulates P-gp activity resulting in a 40% intracellular decrease in the P-gp substrate vinblastine. We have also found that P-gp increases the efflux of the endogenous androgen, dihydrotestosterone (DHT), from prostate cells and leads to decreased androgen regulated gene expression.

CONCLUSIONS

We hypothesize that early in prostate cancer progression, increased expression of YB-1 may increase P-gp activity which may in turn lower androgen levels in the prostate tumor cells. Suppression of androgen levels may activate cell survival pathways and lead to an adaptive survival advantage of androgen independent prostate cancer cells following androgen ablation therapy.

P-glycoprotein increases the efflux of the androgen dihydrotestosterone and reduces androgen responsive gene activity in prostate tumor cells

BACKGROUND

P-glycoprotein (P-gp) is commonly associated with multi-drug resistance (MDR) in cancer cells and the efflux of a broad spectrum of chemicals from the cell, including many chemotherapeutics and certain steroid hormones. The impact of P-gp and mechanisms involved in androgen transport and cellular accumulation within normal and malignant prostate cells remains unclear.

METHODS

Following incubation of LNCaP, PC-3, HeLa, and HeLa FLAG-androgen receptor (AR) cells with (3)H-dihydrotestosterone (DHT) alone and in combination with P-gp inhibitors, PSC-833 and verapamil, we examined the cellular accumulation and efflux of androgens, as well as gene transcriptional response.

RESULTS

Our data reveal that the cellular transport and accumulation of DHT is dependent on the expression of functional AR and modulated by P-gp. P-gp over-expression by both transient transfection and aspirin treatment in LNCaP cells showed decreased intracellular DHT accumulation, further suggesting DHT efflux is P-gp regulated.

CONCLUSIONS

Androgen responsiveness may be modulated by P-gp in prostate cancer cells. The biological consequences of increased P-gp expression are decreased androgen accumulation and a corresponding decrease in androgen-regulated transcriptional activity and PSA gene expression.

Antibiotic-dependent correlation between drug-induced killing and loss of luminescence in Streptococcus gordonii expressing luciferase

Measuring antibiotic-induced killing relies on time-consuming biological tests. The firefly luciferase gene (luc) was successfully used as a reporter gene to assess antibiotic efficacy rapidly in slow-growing Mycobacterium tuberculosis. We tested whether luc expression could also provide a rapid evaluation of bactericidal drugs in Streptococcus gordonii. The suicide vectors pFW5luc and a modified version of pJDC9 carrying a promoterless luc gene were used to construct transcriptional-fusion mutants. One mutant susceptible to penicillin-induced killing (LMI2) and three penicillin-tolerant derivatives (LMI103, LMI104, and LMI105) producing luciferase under independent streptococcal promoters were tested. The correlation between antibiotic-induced killing and luminescence was determined with mechanistically unrelated drugs. Chloramphenicol (20 times the MIC) inhibited bacterial growth. In parallel, luciferase stopped increasing and remained stable, as determined by luminescence and Western blots. Ciprofloxacin (200 times the MIC) rapidly killed 1.5 log10 CFU/ml in 2-4 hr. Luminescence decreased simultaneously by 10-fold. In contrast, penicillin (200 times the MIC) gave discordant results. Although killing was slow (< or = 0.5 log10 CFU/ml in 2 hr), luminescence dropped abruptly by 50-100-times in the same time. Inactivating penicillin with penicillinase restored luminescence, irrespective of viable counts. This was not due to altered luciferase expression or stability, suggesting some kind of post-translational modification. Luciferase shares homology with aminoacyl-tRNA synthetase and acyl-CoA ligase, which might be regulated by macromolecule synthesis and hence affected in penicillin-inhibited cells. Because of resemblance, luciferase might be down-regulated simultaneously. Luminescence cannot be universally used to predict antibiotic-induced killing. Thus, introducing reporter enzymes sharing mechanistic similarities with normal metabolic reactions might reveal other effects than those expected.

Development of a dual-luciferase fusion gene as a sensitive marker for site-directed DNA repair strategies

BACKGROUND

Several novel techniques have been developed recently for the site-specific repair of DNA as an approach to gene therapy. Correction efficiencies as high as 40% have been reported, well within the range of therapeutic impact for a number of genetic diseases. Unfortunately, many of the model systems in which these methods have been employed typically target genes that are not well suited for analyzing the various techniques.

METHODS

To address this, we have constructed and characterized a dual-luciferase fusion gene as a sensitive marker for optimizing repair strategies. The genes encoding two distinct luciferase proteins were fused so that expression of one luciferase necessitated expression of the other. Engineering a stop codon in the downstream luciferase gene created an ideal tool to study the efficiency of various site-directed DNA repair techniques as one luciferase can act as an internal control while the other is targeted for correction.

RESULTS

Fusing two luciferase genes resulted in a single protein that produces two bioluminescent activities in a constant ratio. The utility of this system as a target for site-directed DNA repair research was demonstrated using two of the recently developed gene repair techniques, small fragment homologous replacement and oligonucleotide-mediated repair, to mediate correction and by the ability to detect repair efficiencies of less than 5 x 10(-6) (<1 event in 200000).

CONCLUSIONS

The ability to rapidly and accurately quantify the amount of correction using the dual-luciferase fusion system will allow the comparison and evaluation of the many factors involved in successful gene repair and lead to the optimization of these techniques, both in cell culture and in whole animals.

Polychlorinated biphenyls interfere with androgen-induced transcriptional activation and hormone binding

Polychlorinated biphenyls (PCBs) are ubiquitous highly persistent manufactured chemicals known to bioaccumulate in the food chain. Exposure to PCBs has been implicated in a wide range of human health effects, including altering normal endocrine processes and reproductive function. However, very little is understood regarding the specific mechanisms by which PCBs may exert their effects in biological systems. We have examined the ability of PCBs to interfere with transcriptional activation of the androgen receptor (AR) and glucocorticoid receptor (GR) in an in vitro transcription-based reporter assay system. Four Aroclor PCB mixtures were found to antagonize AR-mediated transcription in the presence of the natural AR ligand dihydrotestosterone (DHT). The antagonistic activity of Aroclor mixtures increased in the following order: 1260 < 1242 < 1254 < 1248. These Aroclor mixtures had no discernible effect on GR activity. Aroclor 1254 in the absence of DHT exhibited weak agonistic responses in a dose-dependent manner with AR. Within a series of individual congeners, congeners 42, 128, and 138 are shown to antagonize AR activity. These congeners all share a common core chlorine substitution pattern. Ligand-binding studies demonstrate that endocrine activities of PCB mixtures and congeners on AR are likely due to direct and specific binding to AR ligand-binding domain.

The role of Sp family members, basic Kruppel-like factor, and E box factors in the basal and IFN-gamma regulated expression of the human complement C4 promoter

The fourth component of human complement (C4) is a serum protein that is expressed in the liver and other organs. The promoter region of the C4 gene has been analyzed in reporter gene assays in two cell lines that represent hepatic (HepG2) and monocytic (U937) lineages. Analysis indicated that regions important for basal transcription in HepG2 cells included Sp1 and E box sites within the first 100 bp upstream of the transcription initiation site but not the nuclear factor-1 site important in the control of the mouse C4 gene. Also, a region encompassing -468 to -310 was able to repress activity 2-fold. However, when a CACCC or GT box sequence at -140 was mutated the repressive activity of the upstream region resulted in almost no activity. The -140 region consists of a series of four closely positioned GT boxes that were shown to bind Sp1, Sp3, and basic Krupple-like factor in EMSA. This novel two-part regulatory element may be involved in the regulated expression of C4. However, IFN-gamma a major activator of C4 expression did not signal through this two-part regulatory element. We were able to map the position of an IFN-gamma responsive element in U937. IFN-gamma was able to increase transcription by up to 20-fold with mutations in the E box sequence at -78 to -73, thus completely abolishing induction. We conclude that the E box binding factors, which appear to be distinct from upstream stimulatory factors 1 and 2, are totally responsible for IFN-gamma induction of C4.

Effect of transforming RNA on the synthesis of a protein with a secretory signal sequence in vitro

U5 small nuclear RNA itself can act as a clastogenic and transforming agent when transfected into cells. In the previous work, the 3' half of the U5 small nuclear RNA first stem structure (designated RNA3S) was capable of driving normal cells into tumorigenic cells when expressed with a poly(A) tail (RNA3S+). This transformation critically depended upon the polypurine sequence GGAGAGGAA in RNA3S+. In this work, we first examined the pre-beta-lactamase and luciferase (model secretory and nonsecretory proteins) translation with the in vitro synthesized RNA3S in rabbit reticulocyte lysate. The capped RNA3S with a poly(A) tail suppressed the translation. In addition, the polypurine sequence played a crucial role in affecting the secretory protein synthesis, indicating a primary action of RNA3S+. Further studies revealed that the oligodeoxynucleotides, corresponding to the polypurine and its antisense sequences, directly contacted 28 S rRNA in ribosome and 7SL RNA in signal recognition particle, respectively, and differentially affected the nascent chain elongation of secretory protein synthesis. These results suggest that RNA3S+ blocks a physiological regulatory function played by signal recognition particle and the ribosome in the secretory protein synthesis and support the idea that the transformation might result from a repressed cellular activity.

Evidence for a bidirectional promoter complex within the X gene of woodchuck hepatitis virus

The genetic organization of hepadnaviruses is unusual in that all cis-acting regulatory sequences are located within genes. Thus, in the mammalian hepadnavirus genome, the presurface, surface, and X transcript promoters reside within the polymerase gene while the pregenome transcript promoter is located within the X gene. In this study we have identified two additional promoters within the woodchuck hepatitis virus (WHV) X gene that stimulate production of transcripts in vitro. First, we cloned regions of the WHV X gene into a promoterless expression vector (pGL2) to examine their ability to promote expression of firefly luciferase and mapped a previously unidentified promoter to positions 1475-1625 of the WHV8 genome. Deletion analysis revealed that the essential domain of this promoter, termed the ORF5/deltaX transcript promoter, mapped to nucleotides 1525-1625. Analysis revealed that this transcript initiated at nucleotide 1572 in both human (HuH-7) and woodchuck (WLC-3) hepatoma cell lines. Consistent with this finding, DNA footprinting analysis revealed protection of nucleotides 1567-1578 on the positive strand of the WHV8 genome. The function of this transcript in vivo is unclear, however, it may be used to produce a truncated form of the X protein that initiates at an AUG codon at position 1743-1745 on the WHV8 genome. Next, a second promoter was identified at positions 1625-1975 that was responsible for production of an antisense transcript. The activity of this promoter was comparable to that of the previously characterized surface transcript promoter of WHV in the absence of an enhancer. The antisense transcript promoter resides immediately upstream of open reading frame (ORF) 6, a previously identified ORF on the strand opposite of the known WHV protein-encoding sequences, that is thought to represent a vestigial gene. Analysis indicates that the antisense transcript had multiple start sites: nucleotides 1683 and 1762 on the WHV8 genome when assayed in HuH-7 cells, and nucleotide 1786 when assayed in WLC-3 cells. These data are consistent with footprinting analysis of supercoiled WHV DNA that revealed that the regions encompassing nucleotides 1696-1685, 1781-1766, and 1801-1787 on the negative sense DNA strand were protected from nuclease degradation. It is possible that such a transcript was once used in protein expression in an ancestral virus and may now be used for genetic control of WHV replication and/or gene expression. Overall, these data are consistent with the presence of a bidirectional promoter complex within the WHV X gene.

Irreversible phase transition of firefly luciferase: contrasting effects of volatile anesthetics and myristic acid

Firefly luciferase (FFL) has been used as a lipid-free protein model to study direct interaction of anesthetics with proteins. FFL emits a burst of light when luciferin and ATP are added in the presence of oxygen. Volatile anesthetics inhibited FFL at mM ranges, while myristic acid inhibited it at microM range. Despite the large difference, octanol/water partition coefficients of both myristic acid and halothane are 199. Differential scanning calorimetry (DSC) showed that thermal transition occurred at 38.5 degreesC with excess enthalpy of denaturation of 91.9 kcal mol-1. The transition, however, was irreversible. According to the irreversible transition kinetics, the anesthetic effects were evaluated by the temperature where the irreversible transition is half completed (T1/2). Volatile anesthetics decreased T1/2 at mM ranges, while myristic acid and oxyluciferyladenylate (luciferin competitor) increased it at microM ranges. Luciferin is a heterocyclic carboxylate and acylates AMP. Carboxyl group of myristic acid appears to make a high affinity contact to the luciferin-recognition sites. The induced-fit theory states that binding of substrates induces the enzyme into high-energy transition state. Myristic acid stabilized FFL at the transition state, which resisted thermal denaturation. Anesthetics destabilized FFL by reversibly unfolding the protein into less active intermediate states and promoted irreversible transition when the temperature is elevated.

Preparation of a cell-free translation system from PC12 cell

The postmitochondrial fraction (S10) contains the cellular components essential for translation, and a high-salt wash (HSW) of the ribosomes is enriched in eukaryotic initiation factors. This report describes the preparation of a cell-free translation system utilizing an S10 extract from PC12 cells. The products synthesized from either firefly luciferase mRNA or PC12 cell poly(A) RNAs in the PC12-S10 extract were increased by the addition of the HSW from PC12 cells. Increases in the translation of luciferase mRNA by the addition of PC12-HSW were dose-dependent and also dependent on the time of incubation. The translation of human epidermal growth factor receptor (hEGFR) mRNA could also be detected in the PC12-S10 extract translation system by immuno-precipitation. N-linked glycosylation of the translation products also was observed. The efficiency of translation was altered by the addition of Mg2- or K+, and optimization of the concentrations of these ions was necessary for each mRNA. The translation system made from PC12 cells, then, is capable of the synthesis of proteins of relatively high molecular weight and should be useful for analyzing mechanisms of translational control during proliferation and differentiation of cells from a neuronal lineage.

Luminescence-based systems for detection of bacteria in the environment

The development of techniques for detection and tracking of microorganisms in natural environments has been accelerated by the requirement for assessment of the risks associated with environmental release of genetically engineered microbial inocula. Molecular marker systems are particularly appropriate for such studies and luminescence-based markers have the broadest range of applications, involving the introduction of prokaryotic (lux) or eukaryotic (luc) genes for the enzyme luciferase. Lux or luc genes can be detected on the basis of unique DNA sequences by gene probing and PCR amplification, but the major advantage of luminescence-based systems is the ability to detect light emitted by marked organisms or by luciferase activity in cell-free extracts. Luminescent colonies can be detected by eye, providing distinction from colonies of indigenous organisms, and the sensitivity of plate counting can be increased greatly by CCD imaging. Single cells or microcolonies of luminescent organisms can also be detected in environmental samples by CCD image-enhanced microscopy, facilitating study of their spatial distribution. The metabolic activity of luminescence-marked populations can be quantified by luminometry and does not require extraction of cells or laboratory growth. Metabolic activity, and potential activity, of marked organisms therefore can be measured during colonization of soil particles and plant material in real time without disturbing the colonization process. In comparison with traditional activity techniques, luminometry provides significant increases in sensitivity, accuracy, and, most importantly, selectivity, as activity can be measured in the presence of indigenous microbial communities. The sensitivity, speed, and convenience of luminescence measurements make this a powerful technique that is being applied to the study of an increasingly wide range of ecological problems. These include microbial survival and recovery, microbial predation, plant pathogenicity, phylloplane and rhizosphere colonization and reporting of gene expression in environmental samples.

Evaluation of the use of the luciferase-reporter-gene system for gene-regulation studies involving cyclic AMP-elevating agents

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.

MIP1 alpha nuclear protein (MNP), a novel transcription factor expressed in hematopoietic cells that is crucial for transcription of the human MIP-1 alpha gene

Murine macrophage inflammatory protein 1 alpha (MIP-1 alpha) and its human equivalent (GOS19, LD78, or AT464) are members of the -C-C family of low-molecular-weight chemokines. Secreted from activated T cells and macrophages, bone marrow-derived MIP-1 alpha/GOS19 inhibits primitive hematopoietic stem cells and appears to be involved in the homeostatic control of stem cell proliferation. It also induces chemotaxis and inflammatory responses in mature cell types. Therefore, it is important to understand the mechanisms which control the expression of MIP-1 alpha/GOS19. Previous work has shown that in Jurkat T cells, a set of widely expressed transcription factors (the ICK-1 family) affect the GOS19 promoter. One member, ICK-1A, behaves as a strong negative regulator. In this communication, we provide evidence that the pathway of induction in the macrophage cell line U937 is different from that in Jurkat cells. Furthermore, we show that the ICK-1 binding site does not confer negative regulation in U937 cells. We provide evidence for an additional binding site, the MIP-1 alpha nuclear protein (MNP) site, which overlaps the ICK-1 site. Interaction of nuclear extracts from various cell lines and tissue with the MNP site leads to the formation of fast-migrating protein-DNA complexes with similar but distinct electrophoretic mobilities. A mutation of the MNP site which does not abrogate ICK-1 binding inactivates the GOS19.1 promoter in U937 cells and reduces its activity by fourfold in Jurkat cells. We propose that the MNP protein(s) binding at the MNP site constitutes a novel transcription factor(s) expressed in hematopoietic cells.

Comparison of properties of commercially available crystalline native and recombinant firefly luciferases

Commercially available crystalline native and recombinant firefly luciferases were compared. The two types of luciferase had indistinguishable responses to variation in ATP and luciferin concentrations and to omission of reaction components. The time courses of light production, the responses to nucleotide analogues, and the stability of the enzymes under several storage conditions were identical. The native enzyme had a slightly greater specific activity and was more sensitive to trypsin degradation. These differences are probably attributable to differences in conformation.

Expression and quantification of firefly luciferase under control of Rhizobium meliloti symbiotic promoters

We have tested the use of firefly luciferase for monitoring regulated symbiotic nitrogen fixation gene expression. Broad-host-range plasmids carrying translational fusions of Rhizobium meliloti nifH, fixA and nifA promoters were constructed. Despite low levels of promoter activity the absence of Escherichia coli endogenous luminescence and the high sensitivity of the bioluminescent assay for firefly luciferase allowed rapid screening for functional luciferase expression. Plasmids containing symbiotic promoter-luc fusions were established in R. meliloti. Luciferase activity was detected and measured in both vegetative and symbiotic cells giving comparable results with those obtained by beta-galactosidase assays. In addition, the luciferase assay was quicker, more sensitive and could be carried out with unrestricted cells. Furthermore, bioluminescence was high enough in alfalfa nodules containing nifH-luc fusion to be observed by a dark-adapted eye and photographed.

Firefly luciferase as a reporter enzyme for measuring gene expression in vegetative and symbiotic Rhizobium meliloti and other gram-negative bacteria

A DNA segment carrying a cDNA copy of the luciferase gene (luc) of the North American firefly Photinus pyralis, fused to the lambda PR promoter and expressed in Escherichia coli [de Wet et al., Proc. Natl. Acad. Sci. USA 82 (1985) 7870-7873], was inserted into a broad-host-range plasmid vector and established in a variety of Gram-negative bacteria. Luciferase activity, expressed from the lambda PR promoter, was detected in both intact cells and extracts prepared from cells of strains of Rhizobium meliloti, R. phaseoli, R. fredii, Pseudomonas aeruginosa, Agrobacterium tumefaciens, Acinetobacter calcoaceticus and Azotobacter vinelandii. The highest levels of activity, determined by measurements of both intact cells and extracts, were observed for P. aeruginosa and the three species of Rhizobium examined. Expression of luciferase activity also was relatively high in R. meliloti bacteroids of mature alfalfa nodules. This activity was readily detectable in intact nodules using x-ray film or in extracts prepared from purified bacteroids.

Bioluminescent click beetles revisited

In studying beetle bioluminescence in the early 1960s, Dr. McElroy and his colleagues found that the Jamaican click beetle, Pyrophorus plagiophthalamus, was capable of emitting different colours of light. They further found that the luciferin substrate used by this beetle was the same as that in the firefly, demonstrating that the different colours of bioluminescence were due to differences in the structure of the luciferases. We have recently cloned cDNAs from this beetle species which code for at least four different luciferases. The luciferases are distinguishable by their different colours of bioluminescence when expressed in Escherichia coli. The sequence differences between these different luciferases are few, so the amino acids responsible for the different colours of emission must also be few. Through the construction of hybrid luciferases, by rearranging fragments of the original cDNA clones, we have identified some of these amino acid determinants of colour.

Luciferase of Luciola mingrelica fireflies. Kinetics and regulation mechanism

Biochemical properties, spectral parameters of bioluminescence and reaction kinetics for Luciola mingrelica firefly luciferase are described and analysed. The kinetic scheme of the enzymatic process is proposed and discussed. Allosteric regulation of luciferase activity by ATP and its analogues is considered and binding Mg2+ to luciferase shown to increase its activity. Regulation mechanism of luciferase activity by phospholipids is analysed and choline-containing phospholipids shown to be specific luciferase activators. Some properties of firefly luciferase and the luciferase synthesized during firefly mRNA translation in frog oocytes are compared.

Introduction to beetle luciferases and their applications

All beetle luciferases have evolved from a common ancestor: they all use ATP, O2, and a common luciferin as substrates. The most studied of these luciferases is that derived from the firefly Photinus pyralis, a beetle in the superfamily of Cantharoidea. The sensitivity with which the activity of this enzyme can be assayed has made it useful in the measurement of minute concentrations of ATP. With the cloning of the cDNA coding this luciferase, it has also found wide application in molecular biology as a reporter gene. We have recently cloned other cDNAs that code for luciferases from the bioluminescent click beetle, Pyrophorus plagiophthalamus, in the superfamily Elateroidea. These newly acquired luciferases are of at least four different types, distinguishable by their ability to emit different colours of bioluminescence ranging from green to orange. Unique properties of these luciferases, especially their emission of multiple colours, may make them additionally useful in applications.

Synthesis and pathway of Luciola mingrelica firefly luciferase in Xenopus laevis frog oocytes and in cell-free systems

Poly (A+)RNA was isolated from the lanterns of adult fireflies of L. mingrelica. The poly (A+)RNA was translated in a cell-free translation mixture from rabbit reticulocyte and from Krebs II mouse ascites cells and in Xenopus laevis frog oocytes. The synthesis of the enzymatically active firefly luciferase was demonstrated in all systems. In the cell-free systems a maximal quantity of luciferase is synthesized during the first 1-2 h, then the decreasing activity of luciferase is observed. The optimal concentration of mRNA for translation in the mouse ascites cell extract was found. The kinetics of the synthesis of the luciferase, its pathway and stability in X. laevis oocytes was studied. It was observed that luciferase is secreted from oocytes into the incubation medium.

In memoriam Dr Marlene DeLuca. 1987 O. M. Smith Lecture. Firefly luciferase: mechanism of action, cloning and expression of the active enzyme

The untimely death of Marlene DeLuca in 1987 has deprived the scientific community of an outstanding expert on bioluminescence. Earlier in that year she was honoured as the thirty-ninth recipient of the Otto Mitchell Smith Lectureship Award at Oklahoma State University, Stillwater, Oklahoma. On 20 March 1987 Dr DeLuca presented a scientific lecture entitled 'Firefly Luciferase--Mechanism of Action, Cloning, and Expression of the Active Enzyme' and a popular lecture at the banquet that evening entitled 'Light and Life'. She was selected for her excellence in research, her oral presentation ability, and her personableness. Marlene was the first woman so honoured. To honour Dr Otto M. Smith the Alpha Delta Chapter of Phi Lambda Upsilon, a national chemistry honorary organization, inaugurated The Otto Mitchell Smith Lectureship in 1948 at Oklahoma State University. Former awardees include Nobel Laureates H. C. Brown, Stanford Moore, and Arthur Kornberg and the following prominent biochemists/molecular biologists: Robert A. Alberty, University of Wisconsin; Daniel E. Koshland, Brookhaven National Laboratory; Sol Spiegelman, University of Illinois; Carl Djerassi, Stanford University; and John T. Edsall, Harvard University. The lectureship honours Dr O. M. Smith, who was Director of the Research Foundation, professor, and Head of the Departments of Chemistry and Chemical Engineering. As a tribute to Dr DeLuca's outstanding contribution to bioluminescence we reproduce here the edited text of her Otto Mitchell Smith Lectureship and a selected bibliography of her work on firefly bioluminescence.

Firefly luciferase gene: structure and expression in mammalian cells

The nucleotide sequence of the luciferase gene from the firefly Photinus pyralis was determined from the analysis of cDNA and genomic clones. The gene contains six introns, all less than 60 bases in length. The 5' end of the luciferase mRNA was determined by both S1 nuclease analysis and primer extension. Although the luciferase cDNA clone lacked the six N-terminal codons of the open reading frame, we were able to reconstruct the equivalent of a full-length cDNA using the genomic clone as a source of the missing 5' sequence. The full-length, intronless luciferase gene was inserted into mammalian expression vectors and introduced into monkey (CV-1) cells in which enzymatically active firefly luciferase was transiently expressed. In addition, cell lines stably expressing firefly luciferase were isolated. Deleting a portion of the 5'-untranslated region of the luciferase gene removed an upstream initiation (AUG) codon and resulted in a twofold increase in the level of luciferase expression. The ability of the full-length luciferase gene to activate cryptic or enhancerless promoters was also greatly reduced or eliminated by this 5' deletion. Assaying the expression of luciferase provides a rapid and inexpensive method for monitoring promoter activity. Depending on the instrumentation employed to detect luciferase activity, we estimate this assay to be from 30- to 1,000-fold more sensitive than assaying chloramphenicol acetyltransferase expression.

Photographic detection of luminescence in Escherichia coli containing the gene for firefly luciferase

The gene for firefly luciferase (luc) can be used as a generalized genetic probe. A method that aids in the analysis of shuttle vectors containing luc by allowing verification in Escherichia coli of a functional coding sequence is presented here. Colonies containing a functional form of luc are detected on film after luciferin is added to initiate the luminescent reaction. Two conditions, lowering the pH of the environment and maintaining aerobic conditions, were found to greatly improve the sensitivity of the assay. This technique may be useful in the development of genetic constructs that alter the natural coding sequence of luc, such as in gene fusions.

Firefly luciferase gene: structure and expression in mammalian cells

The nucleotide sequence of the luciferase gene from the firefly Photinus pyralis was determined from the analysis of cDNA and genomic clones. The gene contains six introns, all less than 60 bases in length. The 5' end of the luciferase mRNA was determined by both S1 nuclease analysis and primer extension. Although the luciferase cDNA clone lacked the six N-terminal codons of the open reading frame, we were able to reconstruct the equivalent of a full-length cDNA using the genomic clone as a source of the missing 5' sequence. The full-length, intronless luciferase gene was inserted into mammalian expression vectors and introduced into monkey (CV-1) cells in which enzymatically active firefly luciferase was transiently expressed. In addition, cell lines stably expressing firefly luciferase were isolated. Deleting a portion of the 5'-untranslated region of the luciferase gene removed an upstream initiation (AUG) codon and resulted in a twofold increase in the level of luciferase expression. The ability of the full-length luciferase gene to activate cryptic or enhancerless promoters was also greatly reduced or eliminated by this 5' deletion. Assaying the expression of luciferase provides a rapid and inexpensive method for monitoring promoter activity. Depending on the instrumentation employed to detect luciferase activity, we estimate this assay to be from 30- to 1,000-fold more sensitive than assaying chloramphenicol acetyltransferase expression.

Cloning of firefly luciferase cDNA and the expression of active luciferase in Escherichia coli

A cDNA library was constructed from firefly (Photinus pyralis) lantern poly(A)+ RNA, using the Escherichia coli expression vector lambda gt11. The library was screened with anti-P. pyralis luciferase (Photinus luciferin:oxygen 4-oxidoreductase, EC 1.13.12.7) antibody, and several cDNA clones expressing luciferase antigens were isolated. One clone, lambda Luc1, contained 1.5 kilobase pairs of cDNA that hybridized to a 1.9- to 2.0-kilobase band on a nitrocellulose blot of electrophoretically fractionated lantern RNA. Hybridization of the cloned cDNA to lantern poly(A)+ RNA selected an RNA that directed the in vitro synthesis of a single polypeptide. This polypeptide comigrated with luciferase on NaDodSO4/PAGE and produced bioluminescence upon the addition of luciferin and ATP. A 1.8-kilobase-pair cDNA was isolated by probing the firefly cDNA library with the cDNA from lambda Luc1. This cDNA contained sufficient coding information to direct the synthesis of active firefly luciferase in E. coli.