WO2002077245A1 - Assay for drug-induced recoding - Google Patents
Assay for drug-induced recoding Download PDFInfo
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- WO2002077245A1 WO2002077245A1 PCT/US2002/008909 US0208909W WO02077245A1 WO 2002077245 A1 WO2002077245 A1 WO 2002077245A1 US 0208909 W US0208909 W US 0208909W WO 02077245 A1 WO02077245 A1 WO 02077245A1
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- polyamine
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
- G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
- G01N33/53—Immunoassay; Biospecific binding assay; Materials therefor
- G01N33/5308—Immunoassay; Biospecific binding assay; Materials therefor for analytes not provided for elsewhere, e.g. nucleic acids, uric acid, worms, mites
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- C—CHEMISTRY; METALLURGY
- C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
- C12Q—MEASURING OR TESTING PROCESSES INVOLVING ENZYMES, NUCLEIC ACIDS OR MICROORGANISMS; COMPOSITIONS OR TEST PAPERS THEREFOR; PROCESSES OF PREPARING SUCH COMPOSITIONS; CONDITION-RESPONSIVE CONTROL IN MICROBIOLOGICAL OR ENZYMOLOGICAL PROCESSES
- C12Q1/00—Measuring or testing processes involving enzymes, nucleic acids or microorganisms; Compositions therefor; Processes of preparing such compositions
- C12Q1/68—Measuring or testing processes involving enzymes, nucleic acids or microorganisms; Compositions therefor; Processes of preparing such compositions involving nucleic acids
- C12Q1/6897—Measuring or testing processes involving enzymes, nucleic acids or microorganisms; Compositions therefor; Processes of preparing such compositions involving nucleic acids involving reporter genes operably linked to promoters
Definitions
- the present invention relates generally to assays for determining receding in drug- induced regulation of genes, and, more particularly but not exclusively, to measuring drug- induced recoding in genes involved in regulating cellular polyamine levels.
- "Recoding” has been defined as a phenomenon where the rules for translation decoding are temporarily altered through specific sites and signals built into the mRNA sequence. I. Brierly, Ribosomal Frameshifting on Viral RNAs, 76 J. Gen. Virol. 1885-1892 (1995); R.F. Gesteland & J. Atkins, Recoding: Dynamic Reprogramming of Translation, 65 Annu. Rev. Biochem. 741-768 (1996). In some cases of recoding, special signals are far distant 3' on the mRNA, M.J. Berry et al., Functional Characterization of the Eukaryotic
- RNA viruses such as Moloney murine leukemia virus (MuLV), Y. Yoshinaka et al., Murine Leukemia Virus Protease Is Encoded by the Gag-Pol Gene and Is Synthesized through Suppression of an Amber Termination Codon, 82 Proc. Nat'l Acad. Sci. USA 1618-1622 (1985).
- MoLV Moloney murine leukemia virus
- Y. Yoshinaka et al. Murine Leukemia Virus Protease Is Encoded by the Gag-Pol Gene and Is Synthesized through Suppression of an Amber Termination Codon, 82 Proc. Nat'l Acad. Sci. USA 1618-1622 (1985).
- the system is autoregulatory and depends on the concentration of polyamines.
- S. Hayashi et al. Ornithine Decarboxylase Antizyme:
- -1 frameshifting is used to synthesize the GagPol precursor polyprotein in retroviruses that have gag, (pro), and pol genes in different reading frames (except spumaretroviruses, J. Enssle et al., Foamy Virus Reverse Transcriptase Is Expressed Independently from the Gag Protein, 93 Proc. Nat'l Acad. Sci. USA 4137-4141 (1996)).
- Examples are the mouse mammary tumor virus (MMTN) gag-pro frameshift, T.
- Affinity Probes of RNAs Specific Features and Applications for Mapping of Spermine Binding Sites in Yeast tRNA(Asp) and Interaction of this tRNA with Yeast Aspartyl-tRNA Synthetase, 18 Nucleic Acids Res. 89-95 (1990); L. Frydman et al., Interactions between Natural Polyamines and tRNA: an 15 N NMR Analysis, 89 Proc. Nat'l Acad. Sci. USA 9186- 9190 (1992), and nucleosomes, H.R. Matthews, Polyamines, Chromatin Structure and
- Ornithine decarboxylase is the first and rate limiting enzyme in the formation of putrescine, from which the polyamines, spermidine and spermine, are derived.
- ODC Ornithine decarboxylase
- Ornithine Decarboxylase Activity is Critical for Cell Transformation, 360 Nature 355-358 (1992); J.A. Moshier et al., Transformation of NIH/3T3 Cells by Ornithine Decarboxylase Overexpression, 53 Cancer Res. 2618-2622 (1993); A. Clifford et al., Role of Ornithine Decarboxylase in Epidermal Tumorigenesis, 55 Cancer Res. 1680-1686 (1995).
- ODC inhibitors such as difluoromethylomithine (DFMO) can reduce cellular proliferation and inhibit tumor formation.
- DFMO difluoromethylomithine
- DFMO Difluoromethylomithine
- a naturally occurring regulator of ODC is mediated by a family of proteins called antizymes.
- S. Hayashi et al. Ornithine Decarboxylase Antizyme: a Novel Type of Regulatory Protein, 21 Trends Biochem. Sci. 27-30 (1996).
- Antizyme 1 inhibits ODC by forming a complex, W.F. Fong et al., The Appearance of an Ornithine Decarboxylase Inhibitory Protein upon the Addition of Putrescine to Cell Cultures, 428 Biochim. Biophys. Acta 456-465 (1976); J.S. Heller et al., Induction of a Protein Inhibitor to Ornithine Decarboxylase by the End Products of its Reaction, 73 Proc.
- the level of antizyme mRNA is high even when no protein is detectable, which is in agreement with the antizyme gene carrying a strong constitutively expressed promoter. S.
- Frameshifting of antizyme 1 occurs at a specific site and is stimulated by an adjacent stop codon in the 0 frame, as well as RNA sequences 5' and an RNA pseudoknot 3' of the shift site.
- Fujita et al. A Macromolecular Inhibitor of the Antizyme to Ornithine Decarboxylase, 204 Biochem. J. 647-652 (1982); K. Koguchi et al., Cloning and Sequencing of a Human cDNA Encoding Ornithine Decarboxylase Antizyme Inhibitor, 1353 Biochim. Biophys. Acta 209-216 (1997); C. Koike et al., Sensitivity to Polyamine-induced Growth Arrest Correlates with Antizyme Induction in Prostate Carcinoma Cells, 59 Cancer Res. 6109-6112 (1999); J.
- antizyme frameshifting is an intracellular sensor for polyamine level that controls antizyme expression. Once produced, antizyme activity is further modulated by antizyme inhibitor to tightly regulate the ODC biosynthetic pathway and polyamine transport into and out of the cell.
- antizyme inhibitor to tightly regulate the ODC biosynthetic pathway and polyamine transport into and out of the cell.
- the present invention provides a tissue culture assay for measuring drug induced recoding in regulating cellular polyamines by utilizing the methods and components described herein.
- providing a quantitative method for the analysis of polyamines, polyamine analogues, and other frameshift agonists in cells would be a significant advancement in the art.
- providing an assay for measuring specific ribosomal frameshifting would also be a significant advancement in the art.
- providing DNAs that can be used to quantitatively determine the occurrence of translational frameshifting in cell lines in which such DNAs have been provided would be another significant advancement in the art.
- An illustrative embodiment of the present invention comprises an assay for quantitatively measuring drug-induced recoding in regulating cellular polyamine levels in cells.
- a DNA construct is provided containing the renilla luciferase gene separated by a short cloning site from the firefly luciferase gene, both under the control of a single upstream promoter functional in mammalian cells, such as an SV40, cytomegalovirus (CMV), or eukaryotic polymerase II promoter.
- the cloning site contains a portion of a antizyme gene known to contain the mRNA signals for polyamine stimulated frameshifting with the downstream firefly gene in the +1 position relative to the upstream renilla gene.
- a control construct is also produced with the genes in the same reading frame. Frameshifting efficiencies can be determined by comparing the ratio of firefly to renilla enzymatic activities in parallel cell cultures.
- Another illustrative embodiment of the present invention comprises a plasmid for use in assaying cellular polyamine levels comprising:
- the first reporter comprises renilla luciferase and the second reporter comprises firefly luciferase. In another illustrative embodiment of the invention, however, the first reporter comprises firefly luciferase and the second reporter comprises renilla luciferase.
- Illustrative polyamine-regulated frameshifting sequences that can be used comprise an antizyme 1 or an antizyme 2 polyamine-regulated frameshifting sequence, such as any of SEQ J-D NO: 1 through SEQ ID NO:6, or an antizyme 3 polyamine-regulated frameshifting sequence.
- a promoter positioned and operative for promoting transcription of the upstream and downstream DNA segments
- a polyamine-regulated frameshifting sequence positioned between the upstream DNA segment and the downstream DNA segment such that the second open reading frame is in a different reading frame with respect to the first open reading frame; wherein, after transfection of the plasmid into cultured mammalian cells, an effective amount of polyamine stimulates translational frameshifting such that the first open reading frame and the second open reading frame are translated in the same frame, thereby resulting in increased expression of the second reporter as compared to expression of the first reporter.
- Still another illustrative embodiment of the invention comprises a method of estimating recoding in genes involved in regulating cellular polyamine levels comprising: (a) transfecting a first set of cultured mammalian cells with a first dual reporter assay construct comprising
- this method further comprises treating the first and second sets of cultured mammalian cells such that endogenous levels of polyamines are reduced.
- the endogenous polyamine levels can be reduced by any of several approaches, such as treating the cells with an inhibitor of polyamine biosynthesis or a stimulator of polyamine excretion or catabolism.
- Illustrative inhibitors of polyamine biosynthesis include inhibitors of ornithine decarboxylase, such as difluoromethylomithine (DFMO), and inhibitors of S- adenosyl methionine decarboxylase.
- An illustrative stimulator of polyamine excretion or catabolism comprises spermidine/spermine N'-acetyltransferase (SSAT).
- Still another illustrative embodiment of the present invention comprises a method for screening for small molecules that affect frameshifting in cells, comprising:
- Still another illustrative embodiment of the present invention comprises a method for screening for small molecules that affect polyamine regulation in cells, comprising:
- Yet another illustrative embodiment of the present invention comprises a method for screening for small molecules that affect polyamine regulation in cells, comprising: (a) transfecting a first set of cultured mammalian cells with a first dual reporter assay constmct comprising
- FIG. 2 is a schematic representation of the SV40 promoter, renilla luciferase and firefly luciferase reporter genes, and multiple cloning site of the frameshift reporter plasmid, p2Luc.
- FIGS. 3A-C are bar graphs representing antizyme 1 frameshifting in tissue culture cells in response to the presence (gray bars) or absence (black bars) of DFMO and putrescine
- FIG. 3A spermidine (FIG. 3B), or spermine (FIG. 3C).
- FIG. 4 is a bar graph representing antizyme 2 frameshifting in a mammalian cell line in response to the presence (gray bars) or absence (black bars) of DFMO and spermidine.
- FIG. 5 is a bar graph showing the effects of deletion of the upstream and downstream antizyme 1 and 2 frameshift stimulatory sequences on frameshifting in mammalian cells in the absence of polyamine and DFMO (None), in the presence of 1 mM spermidine (Spd), in the presence of 2.5 mM DFMO (DFMO), and in the presence of 1 mM spermidine and 2.5 mM DFMO (DFMO + Spd); the constructs used were p2Lucazlpkdel (black bars), p2Lucaz2pdkel (light gray bars), p2Lucazlusdel (dark gray bars), p2Lucaz2usdel (white bars).
- FIG. 6 is a bar graph showing the effect of extracellular polyamine addition on intracellular polyamine levels measured in cells grown in standard growth media (None), and growth media supplemented with 1 mM spermidine (Spd), 2.5 mM DFMO (DFMO), or with both DFMO and spermidine (DFMO + Spd); the concentration of measured putrescine (black bars), spermidine (light gray bars), and spermine (medium gray bars) is shown as nmol/10 6 cells.
- FIGS. 7A-B are bar graphs showing the effects of extracellular agmatine (0-16 mM; FIG. 7A) and cadaverine (0-32 mM; FIG. 7B) addition on frameshifting in cells containing an antizyme 1 (medium gray bars), antizyme 2 (hatched bars), or antizyme 3 (black bars) polyamine-regulated frameshifting sequence; controls were exposed to 2.5 mM DFMO.
- ODC means ornithine decarboxylase
- ADC means arginine decarboxylase
- ORF means open reading frame
- polyamine-regulated frameshifting sequence means a frameshifting or shift site and, optionally, associated 5' and/or 3' regulatory signals that affect the efficiency of frameshifting.
- the antizyme 1 polyamine-regulated frameshifting sequence of SEQ ID NO:l includes a frameshifting site (TCCT) at nucleotides 55-58, an upstream or 5' regulatory signal, and a downstream or 3' pseudoknot regulatory signal.
- the polyamine-regulated frameshifting sequence of SEQ ID NO:3 contains a shift site (TCCT) at nucleotides 10-13 and a 3' pseudoknot regulatory signal, but contains no 5' regulatory signal.
- the polyamine-regulated frameshifting sequence of SEQ ID NO:5 contains a shift site (TCCT) at nucleotides 55-58 and a 5' regulatory signal, but contains no 3' regulatory signal.
- reporter means a gene product that can be assayed for determining the amount of gene product produced in a cell containing a DNA coding for the reporter.
- reporters used in an illustrative embodiment of the present invention include renilla and firefly luciferases.
- Other reporters that can be used according to the present invention include ⁇ -galactosidase ( ⁇ -gal), glutathione S-transferase (GST), chloramphenicol acetyl transferase (CAT), green fluorescent protein (GFP) and derivatives thereof such as YFP and
- reporter horseradish peroxidase (HRP), and alkaline phosphatase, and the like.
- HRP horseradish peroxidase
- other possible reporters according to the present invention include proteins that are recognized by secondary molecules.
- An example of such a reporter is streptavidin, which can be quantified by measuring the amount of binding to a biotm-linked enzyme, wherein the enzyme can be readily assayed, such as alkaline phosphatase.
- protein A which can be quantified by measuring the amount of binding to an antibody-linked enzyme, wherein the enzyme can be readily assayed.
- antizyme is a critical regulator of cellular polyamine levels due to its effect on polyamine transport and it ability to target ODC for degradation. Antizyme expression depends upon an unusual +1 translational frameshift mechanism that is regulated by polyamine levels to form an autoregulatory loop.
- FIG. 1 is a schematic diagram depicting the regulation of polyamine levels by the antizyme regulatory loop. Intracellular polyamines control the frequency of a +1 translational frameshift in antizyme genes (indicated by the curved arrow). High levels of the polyamines putrescine, spermidine, and or spermine cause an increase in antizyme frameshifting resulting in an increase in full length active antizyme protein.
- Antizyme protein inhibits ODC and polyamine transport (indicated by the lines with bars at the end). The reduction of intracellular polyamine levels resulting from the antizyme activity consequently lowers antizyme levels, completing an autoregulatory loop.
- a dual reporter assay can quantitatively measure the effect and levels of polyamines on tissue culture cells.
- the assay comprises placing a polyamine-regulated frameshifting sequence between two DNAs that code for reporter proteins, wherein the open reading frame of the downstream reporter DNA is in the +1 reading frame as compared to the open reading frame of the upstream reporter DNA.
- two dual reporter assay constructs are created by placing a portion of an antizyme gene known to contain the mRNA signals for polyamine-stimulated frameshifting between an upstream DNA encoding a first reporter and a downstream DNA encoding a second reporter.
- the first such constmct places the ORF of the downstream DNA in the +1 reading frame relative to the ORF of the upstream DNA.
- the second reporter is expressed only when frameshifting (recoding) takes place.
- the second (control) constmct places the ORF of the downstream DNA in the same or "0" frame relative to the ORF of the upstream DNA.
- SEQ ID NO: 1 and SEQ ID NO:2 which comprise antizyme 1 and 2 polyamine- regulated frameshifting sequences, respectively, were cloned into the Sail and Bam ⁇ I sites of the p2Luc vector (U.S. Patent No. 6,143,502) to produce plasmids p2Lucazl and p2Lucaz2.
- the shift site (TCCT) corresponding to UCCU in the corresponding mRNA, is present at nucleotides 55-58 of each of these sequences.
- Constmcts were also prepared with deletions of the upstream stimulatory sequences of the antizyme 1 polyamine-regulated frameshifting sequence (SEQ ID NO:3) and the antizyme 2 polyamine-regulated frameshifting sequence
- DNA constructs disclosed herein are merely examples of dual reporter constructs comprising two reporter-encoding DNA segments separated by a cloning site containing a polyamine-regulated frameshifting sequence, and that all such constructs are included within the scope of the present invention.
- An illustrative method of constructing the dual reporter constructs of FIG. 2 is by synthesis of the sequences necessary and sufficient for translational frameshifting (the sequences of the top strand of illustrative embodiments are shown in SEQ JD NO:l through SEQ ID NO:6) through the addition of complementary oligonucleotides, such that when annealed the strands will have Sail and BamRl compatible ends.
- These oligonucleotides can be synthesized according to methods well known in the art, such as with an automated synthesizer (e.g., Applied Biosystems model 380C).
- the frameshift sequences are then ligated into Sail and Bam ⁇ l digested p2Luc vector (G. Grentzmann et al., A Dual-luciferase Reporter System for Studying Recoding Signals, 4 RNA 479-486 (1998); U.S. Patent No. 6,143,502). These may be amplified by transformation into E. coli strain SU1675, although any suitable amplification mechanism may be used. It is advantageous to verify that the construct sequences by autothermocycler sequencing of a sample prior to use.
- Cultured mammalian cells are then transfected with the dual constmcts according to methods well known in the art.
- Parallel cell lines are transfected with the +1 reading frame and 0 reading frame constructs according to methods well known in the art.
- the cells are then incubated under varying conditions to test the effect of such conditions on the polyamine regulation.
- Cells are then lysed and the luciferase activity measured by light emission after injection of luminescence substrate, as is well known in the art.
- the ratio of firefly to renilla luciferase activity in cultures transfected with the +1 frame constmct is compared to the ratio of those transfected with the 0 frame constmct as described in Grentzmann, supra. This provides a quantitative assay for measuring the polyamine-induced recoding.
- Example 1 Human embryonic kidney (HEK293) cells were grown as monolayer cultures in Dulbecco's Modified Eagle Media (DMEM) with 1,000 mg/L D-glucose, L-glutamine, and pyridoxine hydrochloride, and 110 mg/L sodium pyruvate supplemented with 10% fetal bovine semm (FBS) and 50 units/ml penicillin/50 ⁇ g/ml streptomycin.
- DMEM Dulbecco's Modified Eagle Media
- FBS fetal bovine semm
- GC-2 mouse germ line
- GC-2 cells had been maintained as a monolayer in DMEM with 4,500 mg/L D-glucose and L-glutamine, 110 mg/L sodium pyruvate and pyridoxine hydrochloride supplemented with 10% FBS, 50 units/ml penicillin/50 ⁇ g ml streptomycin, and 1% nonessential amino acids. All cells were incubated at 37°C in an atmosphere of 5%
- LJJP OFECTIN reagent is a 1 : 1 (w/w) liposome formulation of the cationic lipid
- DOTMA dioleoyl phosphotidylethanolamine
- DOPE dioleoyl phosphotidylethanolamine
- the fresh media with semm, 1 mM aminoguanidine, and varying levels of polyamines or DFMO were added and incubation continued for 12 hours prior to analysis.
- Cells were lysed using passive lysis buffer and luciferase activity was determined using the Dual Luciferase reporter assay (Promega, Madison, Wisconsin) as described in Grentzmann, supra. For all reactions, light emission was measure between 2 and 12 seconds after 100 ⁇ l of luminescence substrate was injected.
- Frameshift efficiency was calculated by comparing the ratio of firefly to luciferase activity in cultures transfected with p2Luc antizyme constmcts and compared to ratios obtained from cultures transfected with p2Luc in- frame control constmcts as described in Grentzmann, supra.
- HEK293 cells were plated in 10 cm dishes with 10 ml of the growth media as described above at a concentration of 3 X 10 5 cells/ml and incubated for 24 hours. The medium was replaced with fresh medium supplemented with 1 mM aminoguanidine and various concentrations of either putrescine, spermidine, or spermine. The dishes were incubated further for 24 hours, placed on ice, washed with phosphate buffered saline twice, drained completely, and cells were dismpted by 3 freeze/thaw cycles.
- cell extract buffer 25mM Tris-HCl, pH 7.2, 1 mM dithiothreitol, 1 mM EDTA, and 0.01% Tween 80
- Antizyme activities were measured as ODC-inhibitory activities that could be reversed by excess antizyme inhibitor.
- Cell extracts 40 ⁇ l were mixed with 2.0 units of mouse kidney ODC in duplicate. To one set, 0.1 ⁇ g of GST-antizyme inhibitor protein was added.
- ODC activity of each mixture was assayed by measuring the release of 14 CO 2 from L-[ 1 - I4 C] ornithine (as described in I.P. Ivanov et al., Discovery of aspermatogenesis Stage-specific Ornithine Decarboxylase Antizyme: Antizyme 3, 97 Proc. Nat'l Acad. Sci. USA 97, 4808- 4813 (2000); I.P. Ivanov et al., Conservation of Polyamine Regulation by Translational Frameshifting from Yeast to Mammals, 19 EMBO J. 1907-1917 (2000); S. Matsufuji et al., Reading Two Bases Twice: Mammalian Antizyme Frameshifting in Yeast, 15 EMBO J.
- Protein concentrations of the extracts were determined with the BCA protein assay kit (Pierce) using bovine semm albumin as a standard.
- One unit of ODC and antizyme was defined as the activity releasing InM CO 2 per hour and the activity inhibiting 1 unit of ODC, respectively.
- Polyamine levels were also measured for comparison. Intracellular polyamine levels were determined by HPLC analysis of whole cell lysates. Cells (3 X 10 5 ) were grown in 6-well plates for 48 hours at 37°C in an atmosphere of 5% CO 2 , either in the presence or absence of DFMO. Cells were then mock transfected as described above.
- Results of this experiment show the present invention to provide an accurate measurement of frameshifting in response to polyamine levels in HEK293 cells grown under various conditions designed to deplete or increase those levels.
- Under standard growth conditions DMEM supplemented with 10% FBS
- approximately 25% of translating ribosomes shifted to the +1 frame.
- a small increase in frameshifting was observed using the dual luciferase reporter system, as shown in FIGS. 3A, 3B and 3C.
- Maximal frameshifting stimulation of approximately 40%, a 1.3 to 1.5 fold increase, was observed at concentrations of 0.01-0.1 mM spermine, 0.1-2 mM spermidine, and 0.5-2 mM putrescine.
- the present invention also accurately determined the extent to which HEK293 cells pre-treated with DFMO were more sensitive to exogenous polyamine addition with regard to the frequency of both antizyme 1 and antizyme 2 frameshifting.
- Antizyme 1 frameshifting levels were measured at approximately 6% after treatment with DFMO for 48 hours and increased nearly 10-fold to a maximum of between 60% and 70% upon addition of 0.1 mM spermine, 2 mM spermidine, and 2 mM putrescine (FIGS. 3A-C).
- Antizyme 2 frameshifting although slightly lower, showed a very similar response to polyamine depletion and addition, as shown for spermidine in FIG. 4.
- Example 2 To determine the effectiveness of the role of sequences flanking the frameshift site in inducing frameshifting levels, dual luciferase constructs were made in which antizyme sequences preceding and following the antizyme 1 and 2 frameshift sites were deleted. As described above, p2Lucazlusdel and p2Lucaz2usdel correspond to the deletion of upstream antizyme sequences. Likewise, p2Lucazlpkdel and p2Lucaz2pkdel correspond to deletions of sequences downstream from the frameshift site that form a pseudoknot in the mRNA.
- Example 3 To measure the effect of DFMO pre-treatment on the intracellular polyamine levels of tissue culture cells, HEK293 cells were grown, as described above, either in the presence or absence of DFMO (2.5 mM) for 48 hours followed by treatment for 8 hours with 1 mM spermidine. The intracellular concentrations of putrescine, spermidine, and spermine were measured as described above for cells grown under each of these conditions. The addition of DFMO to the growth media resulted in decreased concentrations of intracellular putrescine, spermidine, and spermine compared to control cells, as depicted in FIG. 6. Spermidine concentrations were most affected, showing a nearly 98% decrease in concentration.
- the concentrations of putrescine and spermine dropped by 60% and 41% respectively.
- the addition of spermidine (1 mM) to DFMO treated or untreated cells increased spermidine levels by 1.5- and 1.7-fold, respectively, over control cells and restored putrescine and spermine levels to nearly that of control cells. This demonstrates the effectiveness of the using an ODC inhibitor to deplete polyamine levels in examining intracellular polyamine levels.
- Example 4 In this example, the procedure of Example 1 was carried out except that the amount of frameshifting was determined in response to the addition of 0-16 mM agmatine to cultured mammalian cells.
- Agmatine is a polyamine or polyamine analog that does not naturally occur in mammalian cells.
- Cells treated with 2.5 mM DFMO were used as controls.
- the plasmids used for transfecting the cells were p2Lucazl, p2Lucaz2, or p2Luc into which the frameshifting sequence of the antizyme 3 gene was inserted.
- FIG. 7 A shows that in cells transfected with p2Lucazl or p2Lucaz2 the addition of exogenous agmatine significantly increased the amount of frameshifting observed.
- Example 5 In this example, the procedure of Example 4 was carried out except that the small molecule tested was cadaverine. Cadaverine was added to the cells at levels of 0-32 mM. Figure 7B shows that cadaverine was effective for significantly increasing the amount of frameshifting observed in mammalian cells transfected with p2Lucazl or p2Lucaz2. In cells transfected with p2Luc containing the antizyme 3 frameshifting sequence, however, no increase in frameshifting was observed. Therefore, these experiments show that the cultured cell system of the present invention can be used for identifying a small molecule that affects polyamine regulation in such cells.
- an illustrative method of measuring drug induced recoding in the regulation of genes involved in regulating cellular polyamine levels includes:
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Cited By (3)
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WO2003050296A2 (en) * | 2001-12-13 | 2003-06-19 | Aventis Pharma Deutschland Gmbh | Method for determining the activity of ornithine decarboxylase and for identifying effectors of ornithine decarboxylase activity |
WO2007027106A1 (en) * | 2005-08-30 | 2007-03-08 | University Of Otago | Dual-fluorescent reporter construct and assay for measuring translational recoding |
US7482132B2 (en) | 2001-12-13 | 2009-01-27 | Sanofi-Aventis Deutschland Gmbh | Method for determining the activity of ornithine decarboxylase and for identifying effectors of ornithine decarboxylase activity |
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US5744320A (en) * | 1995-06-07 | 1998-04-28 | Promega Corporation | Quenching reagents and assays for enzyme-mediated luminescence |
US6143502A (en) * | 1999-03-31 | 2000-11-07 | University Of Utah Research Foundation | Dual-luciferase reporter system |
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US5744320A (en) * | 1995-06-07 | 1998-04-28 | Promega Corporation | Quenching reagents and assays for enzyme-mediated luminescence |
US6143502A (en) * | 1999-03-31 | 2000-11-07 | University Of Utah Research Foundation | Dual-luciferase reporter system |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2003050296A2 (en) * | 2001-12-13 | 2003-06-19 | Aventis Pharma Deutschland Gmbh | Method for determining the activity of ornithine decarboxylase and for identifying effectors of ornithine decarboxylase activity |
WO2003050296A3 (en) * | 2001-12-13 | 2003-12-11 | Aventis Pharma Gmbh | Method for determining the activity of ornithine decarboxylase and for identifying effectors of ornithine decarboxylase activity |
US7482132B2 (en) | 2001-12-13 | 2009-01-27 | Sanofi-Aventis Deutschland Gmbh | Method for determining the activity of ornithine decarboxylase and for identifying effectors of ornithine decarboxylase activity |
WO2007027106A1 (en) * | 2005-08-30 | 2007-03-08 | University Of Otago | Dual-fluorescent reporter construct and assay for measuring translational recoding |
CN101384720B (en) * | 2005-08-30 | 2012-06-20 | 奥塔哥创新有限公司 | Dual-fluorescent reporter gene construct and assay for measuring translational recoding |
US8389236B2 (en) | 2005-08-30 | 2013-03-05 | Otago Innovation Limited | Assay |
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