WO2003031600A1 - Saccharomyces-cerevisiae-hefestamm mit stabiler integration und expression der nukleinsäuresequenz für einen heterologen kaliumionen-kanal - Google Patents
Saccharomyces-cerevisiae-hefestamm mit stabiler integration und expression der nukleinsäuresequenz für einen heterologen kaliumionen-kanal Download PDFInfo
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- C12N15/87—Introduction of foreign genetic material using processes not otherwise provided for, e.g. co-transformation
- C12N15/90—Stable introduction of foreign DNA into chromosome
- C12N15/902—Stable introduction of foreign DNA into chromosome using homologous recombination
- C12N15/905—Stable introduction of foreign DNA into chromosome using homologous recombination in yeast
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Definitions
- the invention relates to Saccfraromyces-cerew 's / ae yeast strains with a stable integration and expression of the nucleic acid sequence for a heterologous potassium ion channel as well as the method for this yeast strain construction.
- the invention relates to a Sacc ⁇ aromyces cerews / ae yeast strain in which all identified potassium ion translocation systems are specifically deleted; such Saccr / aromyces-cerew 's /' ae yeast strain, coded into the addition, a nucleic acid sequence encoding a heterologous potassium ion channel, in particular for a mammalian potassium ion channel as the human ERG potassium ion channel (HERG) is stably integrated into the yeast genome and expressed; a method of stably integrating heterologous potassium ion channel proteins into a Sacctjaromyces cere ' s / ae yeast strain and a method of detecting specific modulators of mammalian potassium ion channels using said yeast strains.
- a nucleic acid sequence encoding a heterologous potassium ion channel in particular for a mammalian potassium ion channel as the human ERG potassium ion channel (HERG) is stably integrated
- the yeast strains of the present invention are useful for identifying mammalian modulators, including human potassium ion channel genes or their protein products involved in genetic diseases.
- the yeast strains are the basis of a pharmacological screening system of natural and / or chemical libraries with high efficiency for industrial use.
- Modulators of HERG potassium ion channels are valuable pharmacological agents with potential therapeutic anti-arrhythmic and / or anti-fibrillar application.
- Ion channels are transmembrane proteins that selectively mediate the flow of certain ions through membranes.
- potassium ion channels are the most numerous and heterogeneous group. In both excitable and non-excitable cells, they are responsible for maintaining the resting potential.
- the mediated by potassium ion channels Outward currents are the basis of both the shape and frequency as well as the repolarization of action potentials in excitable tissue.
- Potassium ion channels are ubiquitous membrane proteins with a surprising variety of electrical properties. Thus, there are potassium ion channels that rapidly inactivate (A-type channels) and those that mediate inward currents (K channels). The functional diversity of potassium ion channels is reflected as much in the diversity of their structure.
- Kv voltage-dependent potassium ion channels of the so-called Kv family consist of four subunits, with six transmembrane regions and one pore-forming domain being postulated for each subunit.
- S. cerevisiae TOK1 potassium ion channel has been used to find a prototype of a group of potassium ion channels for which a very different topological structure has been proposed by duplicated pore regions (Ketchum, KA et al., Nature 376: 690-695 (1995) )).
- LQT syndrome is a disease related to ventricular repolarization. Delayed repolarization of ventricular myocytes causes prolongation of the QT interval in the electrocardiogram (ECG).
- ECG electrocardiogram
- the LQT syndrome is usually inherited as an autosomal dominant or recessive disease. If the ventricular arrhythmias degenerate to fibrillation (atrial fibrillation), sudden death may result.
- the role of the human ergo (human eag related gene, HERG) potassium ion channel in the heart is of particular interest.
- HERG human eag related gene
- the fast component I Kr is blocked by class III anti-arrhythmic agents such as D-solatol, dofetilide and clofilium.
- the currents mediated by the HERG potassium ion channel channel correspond to the fast I Kr component of the delayed rectifier measured in isolated myocardial cells (Lees-Miller, JP et al., Circ. Res. 81: 719-723 (1997)).
- HERG-mediated potassium ion currents contribute to the shortening of the action potentials at a faster heart rate. Mutations in HERG cause a hereditary form of polymorphic ventricular arrhythmia (torsades des pointes), also known as LQT2 syndrome (Sanguinetti, MC et al., Cell 81: 299-307 (1995); Curran, ME et al., Cell 80: 795-803 (1995), Keating, MT, Sanguinetti, M.C., Science 272: 681-685 (1996)).
- Another syndrome (LQT1) is due to a defect in the Kv-LQT1 gene (Wang, Q. et al., Nat. Genet. 12: 17-23 (1996)).
- Modulators of potassium ion channels are therefore valuable pharmacological agents with potential therapeutic application.
- Highly selective blockers in- hibitors
- potassium channel openers activators
- Additional substances are for potential therapeutic use in acquired or inherited diseases by mutations in potassium ion channels such.
- B. in HERG necessary.
- New substances are commonly tested in mammalian cell lines expressing foreign potassium ion channel genes.
- this method is complicated by the presence of endogenous channels in the cell lines used, and understandably only limited suitable for biotechnological purposes (homologous and heterologous expression of potassium ion channels).
- the disadvantages of using animal cell lines are in particular:
- yeast test systems with G protein-coupled receptors (King, K. Science 250: 121-123 (1990)), cytoplasmic receptors (Metzger, D. et al., Nature 334: 31-36 (1988) Schena, M. and Yamamoto, KR Science 251: 965-967 (1988)), a human ionic channel (VDAC) (Blachly-Dyson, E. et al., J. Bio. Chem. 268: 1835-1841 (1993)), immunosuppressant agents (Foor, F.
- G protein-coupled receptors King, K. Science 250: 121-123 (1990)
- cytoplasmic receptors Metzger, D. et al., Nature 334: 31-36 (1988) Schena, M. and Yamamoto, KR Science 251: 965-967 (1988)
- VDAC human ionic channel
- immunosuppressant agents Faor, F.
- Cells of the yeast Saccharomyces cerevisiae express a double affinity potassium uptake system encoded by the genes TRK1 and TRK2 (Rodriguez-Navarro, A., Ramos, J., J. Bacteriol 159: 940-945 (1984) and Ko, C. and Gaber Biol. 11: 4266-4273 (1991)) and a TOK1 gene-encoded outward rectifying voltage-dependent potassium ion channel for potassium efflux (Ketchum, KA et al., Nature 376: 690-695 (1995)).
- This protein is the only voltage-dependent potassium ion channel in the plasma membrane of S. cerevisiae. S.
- an inwardly rectifying potassium ion channel gene from guinea pigs could be functionally expressed in yeasts (Tang, W. et al., Mol. Biol. Cell 6: 1231-1240 (1995)).
- Saccharomyces cerevisiae strains containing only mutations in the genes TRK1 and TRK2 for potassium transport are not suitable for biotechnological purposes (heterologous expression of potassium ion channel proteins).
- a variety of potassium transport defective mutants have also been generated by simple mutations in haploid laboratory strains. Saccharomyces cerevisiae wild-type strains are diploid organisms with a double set of chromosomes. The modified alleles in haploid strains are thus genetically unstable.
- mutant yeast strains are in particular: no defined genetic background, the phenotypic selection for expressed heterologous potassium ion channel genes is uncertain the expression of heterologous potassium ion channel genes only minimally and under certain conditions affects the growth of the mutant yeast strains, and thus the screening of pharmacologically active substances on heterologously expressed potassium ion channels is difficult.
- the object and the aim of the present invention was to provide the o.
- a genetically defined (isogenic) Saccharomyces cerevisus / ae strain of yeast in which all yeast-specific genes described for transport and channel proteins are specifically deleted, and a general method for granular, targeted integration of mammalian potassium ions
- the human potassium ion channel erg HERG is stably integrated into the yeast genome and functionally expressed.
- yeasts can be used in growth-based assays for screening many different substance libraries on a very small scale and with high efficiency ("screening" methods in microtiter dishes) and as a recombinant system for analyzing and confirming therapeutically active substances on target proteins of human origin. In addition, they can be used as biotherapeutics as well as substrates for targeted drug development.
- This object is achieved by a genetically modified isogenic Saccharomyces cerevisiae yeast strain with deletions in the TRK1, TRK2 and TOK1 genes necessary for potassium uptake, and subsequent integration of nucleic acid sequences encoding heterologous potassium konn channels, in particular for human encode erg potassium ion channel.
- This S, -cerew 's / ae-yeast strain is obtainable by the introduction of one or more selective marker (auxotrophy and / or resistance), followed by crossing to obtain isoge- ner strains and selecting those strains which, after transformation and stable integration of the potassium ion channel gene into the yeast genome (ie, the chromosomally encoded genetic information) and grow in culture media with a limited potassium concentration of 10 mg / l or less.
- the invention thus relates
- a preferred embodiment of the modified S. cerevisae yeast strain of (1) is a modified yeast strain further comprising one or more nucleic acid sequences encoding a heterologous potassium ion channel or a functional derivative or mutation thereof integrated into the yeast genome and expressed;
- a preferred embodiment of the modified S. cerewsae yeast strain of (1) is a modified yeast strain in which, further, selectively only one functional heterologous nucleic acid sequence is stably integrated into a single locus in the yeast genome;
- a process for producing a modified Saccharomyces cerevisiae yeast strain as defined in (2), comprising transforming a parent yeast strain or yeast strain as defined in (1) with an integration vector encoding a nucleic acid sequence encoding the potassium ion channel comprises;
- a method of detecting specific modulators of the mammalian potassium ion channel comprising: a) treating a Saccharomyces cerevisiae yeast strain as defined in (2) or (3) with test substances, b) determining growth in the presence or after application of a Test substance, c) measurements of the increase or decrease in potassium ion transport of those strains in the presence or after application of a test substance;
- a method for the directed singular integration of a funktionelllen HE terolgen nucleic acid sequence in a singular locus of Saccharomyces cerew 's /' ae-yeast genome comprising transforming a Popefestammes with an integration vector comprising a nucleic acid construct from the to be integrated functional nucleic acid sequence and a promoter effective in S. cerevisiae flanked by nucleobic acid sequences homologous to the unique gene locus in S. cerevisiae; and
- Fig. 1 shows a schematic representation of the genomic fragments containing the Saccharomyces cerevisiae wild type TRK1, TRK2 and TOKl loci and the corresponding mutant alleles trkl :: ⁇ 51lox-kanMX, trk2 ⁇ 50 :: lox-kanMX and tokl ⁇ l :: lox-kanMX (cf. Clarification, the kan R gene is not drawn to scale, the size of this gene is 1.0 kb).
- the TRK1, TRK2 and TOK1 coding regions are indicated by black bars.
- the mutant alleles were used to replace the corresponding wild-type loci in sacca romyces cerevisiae strains transformed.
- TRK1-sense SEQ ID NO: 1
- TRK1-antisense SEQ ID NO: 2
- TRK2-sense SEQ ID NO: 3
- TRK2-antisense SEQ ID NO: 4
- TOK1sense SEQ ID NO: 5
- TOK1 antisense SEQ ID NO: 6
- Fig. 2 shows a listing of the primers used; * Position numbers refer to either 5 'upstream (-) of the START codon or 3 downstream to the STOP codon.
- the underlined sequences correspond to the amino glycoside phosphotransferase sequences in plasmid pUG6 (described in Güldener, U., et al., Nucleic Acid Research 24: 2519-2524 (1996)).
- Fig. 3 is a list of constructed Saccharomyces cerevisiae strains.
- Fig. 4 shows a schematic representation of the plasmid construct p679-pmal-HERG which was used to express the human erg potassium ion channel.
- the pmal (Saccharomyces cerevisiae plasma membrane ATPase) promoter sequence and the nucleic acid sequence for the human erg potassium ion channel (HERG) are shown as filled arrows.
- the plasmid construct has the following functional regions: Amp (start: 1268, end: 2125 (complement)); HIS3 (Start: 2709; End: 3371); fl (+) (start: 3585; end: 4041 (complement)); lacZ (start: 4043; end: 4231 (complement)); Ieu2 5 '(integration sequence) (start: 4242; end: 4719 (complement)); Leu2 3 '(integration sequence) (start: 4728; end: 5347 (complement)); pmal promoter (start: 5378; end: 6316); HERG (coding region) (start: 6326; finish: 9802); Linearization (Notl) (start: 4720, end: 4727); lacZ promoter (start: 109; end: 231 (complement)); ColEl (start: 325; end: 1205).
- the nucleic acid sequence of the plasmid is shown in SEQ ID NO: 28.
- Figure 5B shows the S. cerevisiae chromosomes X gene (5729 bp) comprising TRK1 (ACCESSION No. Z49404 Y13136; Submitted (25-SEP-1995) from the Max Planck Institute of Biochemistry, Am Klopferspitz 18a D-82152 Martinsried; CDS component (1232..4939); SEQ ID NO: 11).
- the TRK1 protein is shown in Figure 5A (SEQ ID NO: 12).
- Figure 6B shows the S. cerevisiae TRK2 gene (Accession No. M65215; Mol. Cell Biol. 11, 4266-4273 (1991); CDS 920..3589; SEQ ID NO: 13).
- the TRK2 protein is shown in Figure 6A (SEQ ID NO: 14).
- Figure 7B shows the Saccharomyces cerevisiae "outward-rectifier potassium Channel Toklp" (TOK1) gene (Accession No. U28005; Yeast 10 (7), 965-973 (1994); Submitted (30-May-1995) Karen A. Ketchum, Boyer Center for Molecular Medicine, Yale University, 295 Congress Avenue, New Haven, CT 06536-0812, USA, CDS 30..2105, SEQ ID NO: 15).
- the Tokl protein is shown in Figure 7A (SEQ ID NO: 16).
- Figure 8A shows the human putative potassium channel subunit (HERG) gene (Accession No. U04270; Proc. Natl. Acad., See, USA (1994); submitted (09-Dec-1993) to Jeffrey W. Warmke, Genetics and Molecular Biology, Merch Search Laboratories, 126 East Lincoln Avenue, PO Box 2000, Rahway, NJ 07065, USA; CDS 184..3663; SEQ ID NO: 17)
- the HERG protein is shown in Figure 8B (SEQ ID NO: 18 ).
- Figure 9 shows the results of the "reverse transcription" polymerase chain reaction of Example 4.2 (A: RNA, 2nd clone 5, 3rd clone 6, 4th clone 7, 5th clone 8, 6th clone 10, and B: 1 2. markers; 2. clone 5; 3. clone 6; 4. clone 7; 5. clone 8; 6. clone 10; 7. RNA control; 8. Construct control; 9th water control).
- Fig. 10 shows the growth of the isolated Trkltrk2tokl Saccharomyces cerevisiae triple mutant with defective potassium ion transport depending on the potassium ion concentration in the culture medium.
- Figure 11 shows the vector p77-TOK-pmal (7429 bp). The exact DNA sequence is shown in SEQ ID NO: 27.
- all potassium ion translocation genes are including TRKl, TRK2 and TOKl deleted or disruptered.
- the yeast strain is preferably a trkl + trk2 + tokl mutant.
- TRKl, TRK2 potassium transport proteins
- TOKl potassium ion channel
- the selectable biosynthetic marker genes (auxotrophy needs and / or resistances) can be introduced into the loci of the wild-type potassium transporter genes by recombinant DNA techniques. Suitable selectable markers are e.g. the auxotrophic markers URA3 and LEU2 or genes showing resistance e.g. against G418 (aminoglycoside phosphotransferase gene) effect. Such modified alleles can then be transformed into Saccharomyces cerevisiae, where they replace the wild-type loci by homologous recombination. The strains with modified alleles can be determined by selection for the biosynthetic marker (s).
- the selectable biosynthetic markers introduced into the loci of the potassium translocation systems also provide an easy way to transfer these mutations into genetically different lines (crossing).
- a strain containing a mutation in one of the potassium translocation genes e.g., TRK1 or TRK2 or TOK1
- TRK1 or TRK2 or TOK1 can be crossed to diploids with a strain of the opposite mating type carrying a mutation in another potassium translocation gene (e.g., TRK2 or TRK1 or TOK1).
- TRK2 or TRK1 or TOK1 By subsequent sporulation into haploids (tetrad analysis), the isogenic progeny can then be selected for the presence of the biosynthetic markers.
- the trkltrk2tokl triple-mutant Saccharomyces cerevisiae phenotype can be determined by growth tests on selective culture media with potassium concentrations of 10 mM or less.
- a yeast strain according to embodiments (1) to (3) according to the invention can be determined by a test which analyzes whether the expressed potassium ion channel gene to be tested functionally complements the trkltrk2tokl triple mutant Saccharomyces cerevisiae phenotype.
- the modified yeast strains of the embodiments (2) and (3) are obtained by transforming the Saccharomyces cerevisiae yeast strain of the present invention with a recombinant DNA containing the gene of the potassium ion channel or functional heterologous nucleic acid sequence to be expressed also can code for a heterologous potassium ion channel) contains.
- "Heterologous potassium ion channels" in the context of the present invention are those potassium ion channels which are not derived from S.
- the heterologous potassium ion channel be (i) a mammalian potassium ion channel, in particular a human potassium ion channel or a functional derivative or a mutation thereof, and / or (ii) a potassium ion channel containing the Potassium ion uptake, an inbound (K
- HERG erg ergic potassium ion channel
- the yeast strain according to embodiment (3) of the invention is obtainable by directed integration by means of an integration vector into a unique gene locus, wherein the integration vector is a nucleic acid construct of the functional nucleic acid sequence and a promoter effective in Saccharomyces cerevisiae flanked in nucleic acid sequences belonging to the singular gene locus S. cerevisiae are homologous.
- the functional nucleic acid encodes the HERG potassium ion channel, with particular preference being given to integrating HERG at the locus of one of the potassium ion translocation systems, in particular at the TOK1 locus of the yeast genome.
- a further subject of the invention is the construction and transformation of a Saccharomyces cerevisiae yeast strain with a recombinant DNA, which enables targeted integration into a unique gene locus of the yeast genome.
- a Recombinant DNA By transformation of such a Recombinant DNA is transformed into a transgenic yeast strain in which the foreign DNA is stably integrated into the yeast genome, with which chromosomal genetic information is propagated and thus continuously transmitted to the progeny.
- the wild type Saccharomyces cerevisiae phenotype can be determined by selecting those strains that grow in the culture medium after transformation, selection and after cultivation under conditions of 10 mg / l potassium ions. For this purpose, the strain to be tested is incubated by growth tests on selective culture media with potassium ion concentrations of 10 mM or less.
- the integration vector (8) employable for the method according to embodiment (7) comprises a nucleic acid construct (DNA, RNA, etc.) of the functional nucleic acid sequence to be integrated and a promoter effective in S. cerevisiae flanked by nucleellic acid sequences homologous to the unique gene locus in S. cerevisiae.
- a nucleic acid construct DNA, RNA, etc.
- a promoter effective in S. cerevisiae flanked by nucleellic acid sequences homologous to the unique gene locus in S. cerevisiae.
- integration vectors that mediate integration into specific loci of the yeast system are known, e.g. P679 and derivatives (Doheny, K.F. et al., Cell, 73 (4): 761-774 (1993)).
- these vectors were mostly constructed when only part of the yeast genome was known (before 1996).
- Nucleic acid sequence to be integrated in the sense of the present invention are all heterologous, ie not derived from S. cerevisiae, functional nucleic acid sequences that are expressible in S. cerevisiae.
- the heterologous nucleic acid sequences may be derived from mammals (including from humans), plants, but also from other microorganisms. It is particularly preferred that the functional nucleic acid sequence encode a potassium ion channel (as in embodiment (3) of the invention), but this should not be construed as limiting the invention.
- a potassium ion channel as in embodiment (3) of the invention
- the homologous sequences have a length of 40 to 1000 nucleotides, preferably of at least 80 nucleotides and / or
- the promoter is selected from natural promoters of Saccharomyces cerevisiae and in particular the pmal promoter, and / or (iii) the functional nucleic acid sequence encodes one of the potassium ion channels defined above.
- promoters in addition to the pmal promoter, all natural promoters of S. cerevisiae can be used, such as PGK, phosphoglycerate kinase, ADH, alcohol dehydrogenase, G-galactose permease, CUP1 copper permease, etc., and heterologous promoters which have a sufficient expression rate in S. cerevisiae such as CMVL (cytomegalovirus), etc.
- the pmal promoter is particularly preferred.
- the nucleic acid construct of the integration vector may also contain further functional sequences such as markers, leader sequences, etc.
- the unique gene locus is the TOK1 locus and the flanking sequences are from the region pretok 3130 to 3599 of SEQ ID NO: 27 (corresponding to positions -1 to -449, based on the coding T ⁇ d-sequence) and posttok 3608 to 4156 (complement) of SEQ ID NO: 27 (corresponding to positions 2075 to 2604, based on the coding TOK1 sequence).
- the growth defect of the trkltrk2tokl triple mutant Saccharomyces cerevisiae yeast strain can be used to isolate and accumulate potassium ion channel genes from gene libraries (e.g., human cDNA libraries) when the expressed genes complement the mutations in the tri-mutant yeast strain and have a wild-type phenotype the required potassium ion concentration results.
- gene libraries e.g., human cDNA libraries
- potassium ion channels can be identified which, while physiologically described but not yet isolated, are predicted to be presumed potassium ion channels from nucleic acid or amino acid sequence databases.
- several potassium ion channels can be introduced into the triple mutant to test. whether the growth defect is complemented on potassium ion-limited media.
- yeast strain that stably expresses a foreign potassium ion channel heterologously can be used to screen modulators of the respective potassium ion channel.
- a yeast strain that heterologously expresses a foreign potassium ion channel can be used in simple procedures to screen various test substance libraries (chemical and natural substance libraries). These simple methods in which growth changes or increased and / or decreased potassium ion uptake can be monitored by agar plate assays and / or in liquid culture can thus detect specific active substances that modulate potassium ion channel function.
- the screening method may include such changes as metabolic activity, increased growth rate, or increased uptake of potassium ions.
- the screening method may include such changes as decreased growth rate or decreased potassium ion uptake.
- test substances which are used in the method for the detection of specific modulators may be e.g. be synthetic or natural products.
- Natural products include herbal, animal or microbial extracts.
- the invention also relates to a method for detecting specific modulators of the expressed potassium ion channel including the HERG potassium ion channel, wherein a) a Saccftaromyces cereusae strain containing the nucleic acid sequence for the human erg Potassium ion channel (HERG) but not the yeast's own potassium translocation systems TRK1, TRK2 and TOK1 expressed, treated with test substances, b) the growth in the presence or after application of a test substance is determined and c) the increase or decrease in the potassium ion transport of those strains in the presence or after application of a test substance is measured.
- a Saccftaromyces cereusae strain containing the nucleic acid sequence for the human erg Potassium ion channel (HERG) but not the yeast's own potassium translocation systems TRK1, TRK2 and TOK1 expressed, treated with test substances
- b) the growth in the presence or after application of a test substance is determined and c) the increase or decrease in
- This method is suitable for identifying specific modulators of the HERG ion channel.
- the method is suitable for the detection of (i) anti-inflammatory substances, (ii) anti-fibrillatory substances or (iii) anti-inflammatory substances.
- Yeast transformation Saccharomyces cerevisiae strains were transformed according to the lithium acetate method as described by Rothstein, R. (1991) in Methods in Enzymology 194: 281-302.
- flanking homology PCR Polymerase Chain Reaction
- a Saccharomyces cerevisiae yeast strain JRY379 (Reid, JD et al., Receptors and Channels 4: 51-61 (1996)) was used in the first step with the plasmid pGAL-HO (Rothstein, R., in Guide to Yeast Genetics and Molecular Biology , C. Gutie and GR Fink (eds.) Pp. 281-302 Academic Press (1991)) to obtain the opposite mating type in the resulting strain HLY38 (see also Fig. 3).
- PCR polymerase chain reaction
- TRKl-sense 5 X GAA GGA GGG TAT TCT ATT GGC TCT CAA GGA AGT CAT TGC TCC TGA GTA AGC TTC CGC TGC 3 ⁇ (SEQ ID NO: l) and
- TRK2 antisense 5 ⁇ AAT TAC GTT GGC TCT TAT GTA GGT AAA GAG GGG TAA ACT TGC ATA GGC CAC TAG TGG ATC TG 3 ⁇ (SEQ ID NO: 4);
- TOK1-sense 5 ⁇ GGT TCC GGG ACG AAA GAG TTA GTA TTA TTA ATG CCA GCT GAA GCT TCG TAC GC 3 ⁇ (SEQ ID NO: 5) and
- TOK1 antisense 5 ⁇ AGC TCT TCG TCT TCT ACT AGA TTA CCA ACT AAG CAT AGG CCA CTA GTG GAT CTG 3 ⁇ (SEQ ID NO: 6).
- Strain JRY379 (Reid, JD, Receptors and Channels 4: 51-61 (1996)) was transformed separately with each of the deletion cassettes generated from the PCR, and transformed yeast colonies were selected on culture media with the antibiotic G418 (200 ⁇ g / ml, kanamycin sulfate) (Güldener, U., Nucleic Acid Research 24: 2519-2524 (1996)).
- yeast strains HLY39 and HLY40 have replaced the complete coding regions of the TRK1, TRK2 genes by the lox-kanMX-lox module (aminoglycoside phosphotransferase gene; kan) (see also Figures 5A, 5B for TRK1 and 6A , 6B for TRK1).
- the TOK1 gene is not completely replaced by the lox-kanMX-lox module (aminoglycoside phosphotransferase gene, kan R ): 223 nucleotides remain from the coding region after disruption the 5 'coding region and 88 nucleotides of the 3' coding sequence (see also Figs. 7A and 7B).
- lox-kanMX-lox module aminoglycoside phosphotransferase gene, kan R
- TRK1-START 5 ⁇ CGT TCG GGG CTG ACA ACG CA3 ⁇ (SEQ ID NO: 7), TRK2-START: 5 ⁇ CCC GTC CAT TGA GTG CCC GT 3 ⁇ (SEQ ID NO -8), and
- TOK1-START 5 ⁇ CGC ATT CGC GTC TCG TTA CC 3 ⁇ (SEQ ID NO: 9) as 5 'sense starting molecules against the 3' antisense starting molecule
- KAN antisense 5 ⁇ CCT CAG TGG CAA ATC CTA AC T (SEQ ID NO: 10), which lies 358 base pairs within the aminoglycoside phosphotransferase coding region (kan, lox-kanMX-lox module) in plasmid pUG6.
- the yeast strains HLY39, HLY40 and HLY41 contain the trkl ⁇ lr.
- HLY39 trkl ⁇ Sl :: lox-kanMX-lox
- HLY40 trk2 ⁇ 50 :: loxkanMX-lox
- HLY41 tokl ⁇ O :: lox-kanMX-lox
- Figure 3 The isolated strains HLY39 (trkl ⁇ Sl :: lox-kanMX-lox), HLY40 (trk2 ⁇ 50 :: loxkanMX-lox) and HLY41 (tokl ⁇ O :: lox-kanMX-lox) ( Figure 3) were separated with the plasmid pSH47, which transforms the nucleic acid sequence for Cre / oxP recombinase under control of the GAL1 promoter (Güldener, U., Nucleic Acid Research 24: 2519-2524 (1996)).
- Transformed yeast colonies were grown on culture media with galactose to induce the promoter for the Cre / oxP recombinase and isolated from single cell-derived colonies with sensitivity to G418 (kanamycin sulfate).
- G418 kanamycin sulfate
- the lox-kanMX-lox cassette was specifically excised by the activity of the pSH47 plasmid-encoded Cre / o P recombinase.
- the G418 sensitive yeast strains were grown on culture media with 5-fluoro-orotic acid (5FOA) as described in Rothstein, R. (1991). 5FOA-resistant, single-celled colonies were isolated and grown, and the isolated yeast strains (see also Figure 3) HLY42 (trkl ⁇ 51), HLY43 (trk2 ⁇ 50) and HLY44 (tokl ⁇ SO) contain the unlabelled mutations.
- Figure 5 is the deduced amino acid ⁇ (SEQ ID NO: ll; 5A) and the nucleic acid sequence (SEQ ID NO: 12; 5B) of Saccharomyces cerevisiae potassium ion transport protein TRKl shown.
- the underscore highlighted regions correspond to the deleted sequence.
- the START and STOP codons are indicated by boldface and the oligonucleotides used by italics.
- Figure 6 shows the deduced amino acid (SEQ ID NO: 13; 6A) and nucleic acid sequence (SEQ ID NO: 14; 6B) of Saccharomyces cerevisiae potassium ion transport protein TRK2.
- the underscore highlighted regions correspond to the deleted sequence.
- the START and STOP codons are indicated by boldface and the oligonucleotides used by italics.
- Figure 7 shows the deduced amino acid (SEQ ID NO: 15; 7A) and nucleic acid sequence (SEQ ID NO: 16; 7B) of the Saccharomyces cerevisiae potassium ion ion channel protein TOK1.
- the underscore highlighted regions correspond to the deleted sequence.
- the START and STOP codons are indicated by boldface and the oligonucleotides used by italics.
- the engineered yeast strains were prepared according to the Sherman, F. et al. (Methods in Yeast Genetics: A Laboratory Manual, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, 1981). Subsequently, the diploid strains were sporulated and Segreganten isolated with the desired potassium ion transport defects by micromanipulation.
- the strain HLY38 (MATa his3- ⁇ 200 leu2-3,112 trpl- ⁇ 901 ura3-52 suc2- ⁇ 9) and the strain HLY42 (MATa his3- ⁇ 200 leu2-3,112 trpl- ⁇ 901 ura3-52 suc2- ⁇ 9 trkl ⁇ 51) were crossed, the resulting sponges diploid strain and isolates tetrads on culture media with 50 mM KCl. Since the TRK1 gene codes for the high affinity potassium ion transporter in S. cerevisiae, the trkl mutant yeast strain should have a need for growth for potassium ions.
- the diploid yeast strain, each with an unmutated allele of the potassium ion transporters TRK1 and TRK2 grew on all media tested. This growth was used to examine the recessive mutations. Recessive mutations are necessary for complementation with heterologous genes.
- the potassium ion uptake-defective phenotype segregated as expected for two unrelated genes. Three phenotypes were expected and observed with respect to potassium ion scores from this crossover corresponding to the four genotypes: wild type with no defect in the TRK1, TRK2 alleles, trklTRK2 mutant with poor growth on 100 ⁇ M potassium ions, trk2TRK1 mutant of the same phenotype and trkltrk2 mutant with very poor Growth on 100 ⁇ M potassium ions. The trkltrk2 phenotype could be suppressed by growth on culture media with 10 mM potassium ions.
- a trkltrk2 double mutant yeast strain HLY46 (trkl ⁇ 51 trk2 ⁇ 50) with MAT ⁇ mating type was grown from one of the resulting spores and probed with strain HLY44 (MATa his3- ⁇ 200 Ieu2-3,112 trpl- ⁇ 901 ura3-52 suc2- ⁇ 9 tokl ⁇ 50). crossed, the sporulated diploid strain and isolated tetrads on culture media with 50 mM KCl.
- the diploid yeast strain, each with an unmutated allele of the potassium ion transporters TRK1, TRK2 and TOK1, grew on all media tested. This growth was used to examine the recessive mutations.
- trkltrk2tokl triply mutant Saccharomyces cerevisiae yeast strain HLY47 (trkl ⁇ 51 trk2 ⁇ 50 tokl ⁇ 50) are all previously described yeast-own transport and channel proteins TRKl, TRK2 and TOKl specifically deleted (see also Fig. 3).
- the phenotype of this strain is characterized by growth only on culture media containing at least 50 mM potassium ions.
- Example 2 Construction of a plasmid for targeted, singular integration of foreign genes into the S. cerews / ae genome and for expression of these foreign genes in S. cerevisiae
- genomic DNA was first isolated from the Saccharomyces cerevisiae wild strain S288C (ATCC, USA) using standard methods. 1 ⁇ g of this chromosomal DNA was used for a polymerase chain reaction (PCR) with Thermophilus aquaticus DNA polymerase and the following oligonucleotide primers for the amplification of the 5 'noncoding region of the S.
- PCR polymerase chain reaction
- oligonucleotide pretok_sense 5 ⁇ GG GCGGCC GCCTGCAAAT TTATCGAGAC TCTG 3 '(SEQ ID NO: 21), Position -470 to -449 with respect to the coding TOKl sequence, wherein the nucleotides added for cloning reasons are shown in italics and the nucleotides inserted to obtain a Not I site are underlined.
- the DNA amplified by the PCR was separated as a 0.47 kb fragment by agarose gel electrophoresis and isolated from the gel matrix. This DNA was cleaved with the restriction endonucleases Not I and Sac I, separated by agarose gel electrophoresis and isolated from the gel matrix.
- the plasmid vector p774 (Connelly and Heiter (1996) Cell 86, 275-285, 6.59 kb) was also cleaved with the restriction endonucleases Not I and Sac I, the products were separated by agarose gel electrophoresis and the 6.1 kb fragment from the Gel matrix isolated. The DNA fragments thus obtained were ligated. After transformation into bacteria (E.
- tokl / pmal integration cassette for any desired target genes in the singular TOKl locus of the Saccharomyces cerevisiae yeast genome, 1 ⁇ g isolated, chromosomal DNA in a polymerase chain reaction (PCR) with DNA polymerase from Thermophilus aquaticus and the following oligonucleotide primers used for amplification of the 3 'non-coding region of the S. cerevisiae TOK1 gene: oligonucleotide posttok-antisense: 5 ⁇ GG GCGGCC GCCGGGATCG ATGATGTAGG G 3 '(SEQ ID NO: 23),
- Position 2624 to 2604 based on the coding TOKl sequence, wherein the nucleotides added for cloning reasons are shown in italics and the nucleotides inserted to obtain a Not I site are underlined.
- the DNA amplified by the PCR was separated as a 0.56 kb fragment by agarose gel electrophoresis and isolated from the gel matrix. This DNA was cleaved with the restriction endonucleases Not I and Spe I, separated by agarose gel electrophoresis and isolated from the gel matrix.
- the plasmid vector p77-pretok was also cleaved with the restriction endonucleases Not I and Spe I, the products were separated by agarose gel electrophoresis and the 5.95 kb fragment was isolated from the gel matrix. The resulting fragments were ligated. After transformation into bacteria (E. coli XLI-Blue, Stratagene) and incubation at 37 ° C.
- the yeast own promoter of the plasma membrane ATPase PMA1 was used for transcription of any desired human gene in the yeast Saccharomyces cerevisiae.
- the pym promoter constitutively active in Saccharomyces cerevisiae was isolated as an Eco RI / Bam HI 0.9 kb fragment from the plasmid pRS408 (obtained from Dr. A. Goffeau, Universite Catholique de Louvain-Ia-Neuve, Belgium) after separation by agarose gel electrophoresis.
- the 0.9 kb pmal Eco RI / Bam HI was ligated with the Eco RI / Barn HI digested plasmid vector pUC18.
- the resulting plasmid pUC-pmal was confirmed by restriction mapping and sequencing. From this plasmid, the 0.9 kb pmal promoter fragment was obtained with DNA polymerase from Thermophilus aquaticus and the following oligonucleotide primers for the amplification of the regulatory region: Oligonucleotide pmal_antisense:
- the DNA amplified by the PCR was separated as a 0.93 kb fragment by agarose gel electrophoresis and isolated from the gel matrix. This DNA was cleaved with the restriction endonucleases Sal I and Apa I, separated by agarose gel electrophoresis, isolated from the gel matrix and ligated with the plasmid vector p77-TOK cleaved by the restriction endonucleases Sal I / Apa I. After transformation into bacteria (E. coli XLI-Blue, Stratagene) and incubation at 37 ° C.
- Any desired human target genes can be inserted into this constructed integration plasmid. After cleavage with the restriction endonuclease Not I obtain linear DNA fragments which can be used to transform suitable yeast host strains. This results in stable transgenic yeast strains in which the desired target gene is integrated at the unique TOK1 locus in the yeast genome instead of the endogenous TOK1 gene.
- the yeast's own promoter of the plasma membrane ATPase PMA1 is used for transcription of any desired human gene in the generated transgenic Saccharomyces cerevisiae yeast strain.
- the gene for the human ergo potassium ion channel was isolated by cleavage with the restriction endonucleases Bam HI and XbaI as a 3.9 kilobase pair (kb) fragment from the plasmid pcDNAHERG (obtained from Dr. G. Robertson, University of Wisonsin, Madison, USA) and separation by agarose gel electrophoresis.
- yeast's own promoter of the plasma membrane ATPase PMA1 was used for the transcription of a human gene in the yeast Saccharomyces cerevisiae.
- the pym promoter which was constitutively active in Saccharomyces cerevisiae was isolated as an Eco RI / Bam HI 0.9 kb fragment from the plasmid pRS408 (obtained from Dr. A. Goffeau, Universite Catholique de Louvain-Ia-Neuve, Belgium) after separation by agarose gel electrophoresis.
- Plasmid p679pmal HERG was identified by restriction mapping (see Figure 4).
- the human erg gene was stably integrated into the gene locus for the biosynthetic marker LEU2 of the Saccharomyces cerevisiae yeast strain.
- flanking regions of the LEU2 gene are inserted for directional homologous recombination of the cloned insert at the chromosomal locus of the LEU2 gene in Saccharomyces cerevisiae 5 'and 3'.
- the restriction endonuclease Not I introduced a linearization of the plasmid p679pmalHERG at position 2189 between the flanking LEU2 regions.
- the obtained linear 10.2 kb Not I fragment was used after separation by agarose gel electrophoresis to transform the trkltrk2tokl triple mutant Saccharomyces cerevisiae yeast strain in which all previously described yeast own transport and channel proteins TRKl, TRK2 and TOKl are specifically deleted.
- transformants were selected for the biosynthetic marker HIS3 (HIS3 + prototrophy) likewise contained in the plasmid p679. Single-celled colonies were further selected on culture media with potassium ion concentrations less than 10 mM.
- the expression of the human potassium ion channel erg gene complements the Potassium ion transport defective phenotype of trkltrk2tokl triplicate Saccharomyces cerevisiae mutant on culture media with potassium ion concentrations less than 10 mM.
- yeast's own potassium ion transport and channel proteins in this Saccharomyces cerevisiae strain (genotype MATa his3- ⁇ 200 leu2-3,112 trpl- ⁇ 901 ura3-52 suc2- ⁇ 9 trkl ⁇ 51trk2 ⁇ 50 tokl ⁇ 50 leu2 :: pmalHERG HIS3) (see also FIG human HERG potassium ion channel expressed.
- Figure 8 shows the nucleic acid (SEQ ID NO: 17; 8A) and deduced amino acid sequence (SEQ ID NO: 18; 8B) of the human erg potassium ion channel gene (HERG). The sequence corresponds to that described in the original publication by Trudeau, MC et al., Science 269: 92-95 (1995).
- oligonucleotides used for RNA analysis H1119 5 l CAG CGG CTT GCT CAA CTC CA 3 (SEQ ID NO: 19) and H1557 5 GAT GAG GTC CAC CAC AGC CA 3 '(SEQ ID NO: 20) are indicated by italics and underline.
- FIG. 9 shows the results of a "reverse transcription" polymerase chain reaction.
- RNA was isolated from several positive clones expressing the human potassium ion channel erg gene (clones Nos. 5, 6, 7, and 8) after selective growth in the culture medium with 10 mM potassium ions. The separation of the total RNA for checking the integrity and proportions was carried out in 1% denaturing agarose gel (left part in FIG. 9). This total RNA was transcribed into complementary DNA with reverse transcriptase and amplified in a subsequent PCR analysis using erg specific oligonucleotides (SEQ ID NO: 19) / (SEQ ID NO: 20) a 440 base pair long fragment.
- SEQ ID NO: 19 erg specific oligonucleotides
- SEQ ID NO: 20 a 440 base pair long fragment.
- Non-rewritten RNA from clone # 6 was used to control for possible DNA contamination in the RNA preparation.
- to Control of the correct amplification product was 20 pg of the plasmid p679pmalHERG used.
- To control the reaction mixture a reaction without template was carried out (water control). The separation of the fragments took place in a 0.8% agarose gel.
- RNA analysis by RT-PCR confirmed the expression of the human potassium ion channel erg gene (HERG) introduced by homologous recombination into the trkltrk2tokl triple mutant Saccharomyces cerevisiae yeast strain.
- HERG human potassium ion channel erg gene
- the Saccharomyces cerevisiae yeast strain with defects in all potassium ion translocation systems TRK1, TRK2 and TOK1 does not grow at low potassium ion concentrations (10 mM) in the medium at pH 5.0 and pH 5.5.
- the strain expressing the human potassium ion channel erg gene is able to grow comparably well to 10 mM potassium ions in the medium at pH 5.0 and pH 5.5, the Saccharomyces cerevisiae wild strain.
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WO2001051519A2 (de) * | 2000-01-11 | 2001-07-19 | Aventis Pharma Deutschland Gmbh | Kalium-kanal-mutanten der hefe saccharomyces cerevisiae und deren verwendung für das screening von eukaryotischen kaliumkanälen |
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WO2001051519A2 (de) * | 2000-01-11 | 2001-07-19 | Aventis Pharma Deutschland Gmbh | Kalium-kanal-mutanten der hefe saccharomyces cerevisiae und deren verwendung für das screening von eukaryotischen kaliumkanälen |
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Title |
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FAIRMAN C ET AL: "POTASSIUM UPTAKE THROUGH THE TOK1 K+ CHANNEL IN THE BUDDING YEAST", JOURNAL OF MEMBRANE BIOLOGY, NEW YORK, NY, US, vol. 168, no. 2, 15 March 1999 (1999-03-15), pages 149 - 157, XP001006332 * |
FLOY DOHENY K ET AL: "IDENTIFICATION OF ESSENTIAL COMPONENTS OF THE S. CEREVISIAE KINETOCHORE", CELL, CELL PRESS, CAMBRIDGE, NA, US, vol. 4, no. 73, 21 May 1993 (1993-05-21), pages 761 - 774, XP001071223, ISSN: 0092-8674 * |
SIKORSKI R S ET AL: "A SYSTEM OF SHUTTLE VECTORS AND YEAST HOST STRAINS DESIGNED FOR EFFICIENT MANIPULATION OF DNA IN SACCHAROMYCES CEREVISIAE", GENETICS, GENETICS SOCIETY OF AMERICA, AUSTIN, TX, US, vol. 122, May 1989 (1989-05-01), pages 19 - 27, XP002912109, ISSN: 0016-6731 * |
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