WO2016106504A1 - 表达元件、表达盒、及含其的载体 - Google Patents

表达元件、表达盒、及含其的载体 Download PDF

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WO2016106504A1
WO2016106504A1 PCT/CN2014/095340 CN2014095340W WO2016106504A1 WO 2016106504 A1 WO2016106504 A1 WO 2016106504A1 CN 2014095340 W CN2014095340 W CN 2014095340W WO 2016106504 A1 WO2016106504 A1 WO 2016106504A1
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seq
expression
gene
aforementioned
sequence
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林俊宏
王志鹏
陈正文
方健宇
曾晧真
赖建逢
黄文正
宣诗玲
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财团法人农业科技研究院
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Priority to JP2017531712A priority Critical patent/JP6640226B2/ja
Priority to PCT/CN2014/095340 priority patent/WO2016106504A1/zh
Priority to US15/520,680 priority patent/US10704051B2/en
Priority to TW103146225A priority patent/TWI567197B/zh
Publication of WO2016106504A1 publication Critical patent/WO2016106504A1/zh

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    • C12N15/00—Mutation or genetic engineering; DNA or RNA concerning genetic engineering, vectors, e.g. plasmids, or their isolation, preparation or purification; Use of hosts therefor
    • C12N15/09—Recombinant DNA-technology
    • C12N15/63—Introduction of foreign genetic material using vectors; Vectors; Use of hosts therefor; Regulation of expression
    • C12N15/67—General methods for enhancing the expression
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
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    • C12N15/00—Mutation or genetic engineering; DNA or RNA concerning genetic engineering, vectors, e.g. plasmids, or their isolation, preparation or purification; Use of hosts therefor
    • C12N15/09—Recombinant DNA-technology
    • C12N15/63—Introduction of foreign genetic material using vectors; Vectors; Use of hosts therefor; Regulation of expression
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12N—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA
    • C12N15/00—Mutation or genetic engineering; DNA or RNA concerning genetic engineering, vectors, e.g. plasmids, or their isolation, preparation or purification; Use of hosts therefor
    • C12N15/09—Recombinant DNA-technology
    • C12N15/63—Introduction of foreign genetic material using vectors; Vectors; Use of hosts therefor; Regulation of expression
    • C12N15/70—Vectors or expression systems specially adapted for E. coli
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
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    • C12N2840/00—Vectors comprising a special translation-regulating system
    • C12N2840/002—Vectors comprising a special translation-regulating system controllable or inducible

Definitions

  • the present invention relates to an expression element, and more particularly to an expression element of an arabinose-inducible expression system.
  • the expression system consists of a host cell and a genetic element such as transcription and translation signals, regulatory factors, genes and plasmids.
  • a variety of eukaryotic and prokaryotic expression systems have been established and even commercialized.
  • E. coli In the expression system, the research results and development experience of Escherichia coli expression system are the most abundant, and the genetic manipulation technology and fermentation technology related to this system are very well developed. Advantages of producing recombinant proteins in E. coli include simple gene manipulation, easy culture, rapid growth, high density culture in an inexpensive medium, expression vector and improved host such as protease deficiency strain (protease) Deficient strain) has high selectivity, high protein yield and short production time.
  • protease deficiency strain protease deficiency strain (protease) Deficient strain
  • E. coli expression systems are currently available, such as the trc expression system, the T7 expression system, and the pBAD expression system.
  • the pBAD expression system is an arabinose-inducible expression system composed of an expression vector containing an arabinose-inducible expression element and a regulatory gene in combination with an E. coli host.
  • the advantages of the expression system are: (1) tightly regulating gene expression and avoiding The toxicity caused by the leakage expression of certain genes; (2) the cost of using arabinose as an inducer is relatively low; (3) the amount of protein expression can be regulated by the concentration of arabinose.
  • Another object of the present invention is to provide a vector comprising the aforementioned expression cassette and suitable for use in an arabinose-inducible expression system, thus providing a novel alternative to the field of application of the arabinose-inducible expression system.
  • an expression element of an arabinose-inducible expression system comprising: a promoter and at least one of the following elements:
  • a ribosome binding site having the sequence set forth in SEQ ID NO: 01;
  • T7 phage translational enhancer element having the sequence set forth in SEQ ID NO:08.
  • the present invention further provides an expression cassette comprising: the aforementioned expression element, a start code, a gene to be expressed, and a termination code.
  • the invention further provides a vector comprising: the aforementioned expression cassette and multiple selection sites.
  • the -10 portion of the aforementioned promoter has the sequence shown in SEQ ID NO:06.
  • the -16 portion of the aforementioned promoter has the sequence set forth in SEQ ID NO:07.
  • the aforementioned ribosome binding site has the sequence set forth in SEQ ID NO: 02, SEQ ID NO: 03, SEQ ID NO: 04, SEQ ID NO: 05, or a combination thereof.
  • the aforementioned expression element has: SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 16, SEQ ID NO: 17, SEQ ID NO: 18, SEQ ID NO: 19. SEQ ID NO: 20, SEQ ID NO: 21, or a combination thereof.
  • the aforementioned start code and the gene to be expressed are provided with a downstream sequence; wherein the aforementioned downstream sequence has SEQ ID NO: 09, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: The sequence shown by or a combination thereof.
  • the aforementioned expression cassette further comprises a regulatory gene.
  • the aforementioned regulatory gene is an arabinose-induced expression regulatory gene araC.
  • the gene to be expressed is a gene translated into a green fluorescent protein, an enzyme gene, an antigen gene, a gene having a physiologically active peptide and protein, or a combination thereof.
  • the aforementioned vector further comprises a replication initiation region, a selection gene, a signal peptide, or a combination thereof.
  • the vector comprises a screening gene: a drug resistance screening gene, a non-drug resistance screening gene, or a combination thereof.
  • the present invention provides an expression element and expression cassette for an arabinose-inducible expression system to construct a vector.
  • the aforementioned vector expresses the protein to be expressed by the E. coli system, and has an effect of increasing the expression amount for the gene to be expressed. Accordingly, the present invention provides an expression vector as another novel alternative in the field of genetic engineering.
  • Figure 1 shows a comparison of the sequences of the expression elements in the examples of the present invention.
  • the present invention is intended to provide an expression element which is suitable for an arabinose-inducible expression system and which contributes to an increase in the expression level of a gene to be expressed.
  • the expression element of the present invention By using the expression element of the present invention, the conventional arabinose expression system can be made more industrial value.
  • One aspect of the present invention is to provide an expression element.
  • the aforementioned expression element comprises a promoter and at least one of the following elements: a ribosome binding site or a T7 phage translation enhancing element.
  • the "expression element" as used in the present invention refers to a nucleotide sequence related to gene expression upstream of the start code.
  • the expression element comprises: a promoter (containing a -10 site, a -16 site, and/or a -35 site), a ribosome binding site, a gene expression regulatory sequence, or a combination thereof.
  • the type of the aforementioned promoter is not limited, and those skilled in the art can select a suitable promoter according to their needs.
  • the aforementioned "promoter” is a promoter of araB, so that the aforementioned expression element can be applied to an arabinose-inducible expression system.
  • the -10 portion of the aforementioned promoter has the sequence set forth in SEQ ID NO:06.
  • the -16 portion of the promoter contained in the aforementioned expression element has the sequence shown in SEQ ID NO:07.
  • the "ribosomal binding site" as used in the present invention refers to a sequence which can be recognized and bound by ribosomes during translation.
  • the aforementioned ribosome binding site has SEQ ID NO:01.
  • the aforementioned ribosome binding site has the sequence set forth in SEQ ID NO: 02, SEQ ID NO: 03, SEQ ID NO: 04, SEQ ID NO: 05, or a combination thereof.
  • the "T7 phage translation enhancing element" referred to in the present invention is a nucleotide sequence derived from the upstream of the phage T7 gene No. 10 gene.
  • the aforementioned T7 phage translation enhancing element has the sequence set forth in SEQ ID NO:08.
  • Still another aspect of the present invention is to provide an expression cassette comprising the aforementioned expression element, a start code, a gene to be expressed, and a termination code.
  • the start sequence and the gene to be expressed are provided with a downstream sequence; wherein the aforementioned downstream sequence has SEQ ID NO: 09, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 12, or a combination thereof.
  • the aforementioned expression cassette further comprises a regulatory gene.
  • the "regulatory gene” as used in the present invention refers to a DNA sequence which can translate a gene expression regulating protein.
  • the aforementioned regulatory gene is: araC.
  • the "gene to be expressed” described in the present invention may vary depending on the needs of the user.
  • the aforementioned gene to be expressed is, for example, but not limited to, a gene for transducing a green fluorescent protein, an enzyme gene, an antigen gene, a gene of a physiologically active peptide and protein, or a combination thereof.
  • the "starting code” as used in the present invention refers to a codon that is initially translated in an mRNA. In a possible implementation, the foregoing starting code is: ATG.
  • the "termination code” as used in the present invention refers to a codon that terminates translation. In a possible implementation, the foregoing termination code is: TAA, TAG, or TGA.
  • Another aspect of the present invention is to provide a vector comprising the aforementioned expression cassette and multiple selection sites.
  • the vector further comprises a replication initiation region, a selection gene, a signal peptide, or a combination thereof.
  • the aforementioned multiple selection site comprises more than one nucleotide sequence that can be recognized by the restriction enzyme.
  • the aforementioned restriction enzymes include, but are not limited to, BamHI, BglII, EcoRI, HindIII, NdeI, PstI, SalI, SpeI, XbaI, XhoI, XmaI, or a combination thereof.
  • the "screening gene” referred to in the present invention is used to confirm whether or not the aforementioned vector has been smoothly transformed into a host.
  • the aforementioned screening genes can be, but are not limited to, a drug resistance screening gene, a non-drug resistance screening gene, or a combination thereof.
  • drug resistance screening gene means that the transformation of the vector is confirmed by the resistance to antibiotics.
  • the aforementioned drug resistance screening gene is a tetracycline resistance gene.
  • a host e.g., E. coli
  • E. coli that successfully transforms the vector can produce resistance to tetracycline and survive in an environment containing tetracycline.
  • non-drug resistant screening gene refers to a gene which is not confirmed by resistance to antibiotics.
  • the aforementioned non-drug resistance screening gene is, for example but not limited to, a nucleic acid sequence of ⁇ -galactosidase.
  • the successfully transformed strain will X-gal (5-bromo-4-chloro-3-indolyl- ⁇ -D-pyran) Galactoside is decomposed into galactose and 5-bromo-4-chloro-3-hydroxyindole, while 5-bromo-4-chloro-3-hydroxyindole is dimerized to 5,5'-dibromo-4 , 4'-dichloroindole blue, thus producing an insoluble and recognizable blue substance.
  • the non-drug resistant screening gene is a complementary gene of a nutritionally deficient strain (eg, a thymidylate synthase gene, an amino acid synthesis-related gene, a carbohydrate synthesis-related gene, and a nicotinic adenine dinuclear nucleus).
  • a gene related to the synthesis of a glycosidic acid e.g., a thymidylate synthase gene, an amino acid synthesis-related gene, a carbohydrate synthesis-related gene, and a nicotinic adenine dinuclear nucleus.
  • a gene related to the synthesis of a glycosidic acid e.g, a thymidylate synthase gene, an amino acid synthesis-related gene, a carbohydrate synthesis-related gene, and a nicotinic adenine dinuclear nucleus.
  • a gene related to the synthesis of a glycosidic acid
  • Example 1 Construction and transformation of the arabinose-inducible expression vector of the present invention
  • the expression elements of the original arabinose-inducible expression system were obtained, and the promoter-10 site, the promoter-16 site, and the ribosome binding site (Shen) were repaired. Ornamental, or additional addition of the T7 phage translational enhancer sequence (T7) and/or downstream sequences.
  • T7 phage translational enhancer sequence T7 phage translational enhancer sequence
  • the aforementioned expression element is ligated to pRPSJ-GFPT, pARABM7-GFPT or pARABM11-GFPT to constitute an expression vector of the present invention.
  • the enhanced green fluorescent protein gene was used as a reporter gene to express the gene to be expressed by the E. coli expression system.
  • Table 1 The expression elements produced in this example are shown in Table 1 below:
  • Amplification of the original arabinose-inducible expression element was carried out using the AraCF and AraWR (GATATACATATGTTCACTCCATCCAAAAAAACGGGT; SEQ ID NO: 46) primer combinations using the chromosome of Escherichia coli ECOS 9-5 as a template.
  • PCR polymerase chain reaction
  • the PCR reaction conditions were 96 ° C for 5 minutes (1 step); 94 ° C for 30 seconds, 55 ° C for 30 seconds, 68 ° C for 1 minute (35 cycles); 68 ° C for 5 minutes (1 step).
  • the PCR product was recovered by PCR- MTM Clean Up system, bound to pJET1.2 plasmid by T4 DNA ligase, and the sequence was confirmed to be correct by DNA sequencing, and the plasmid was named pJET-ARABW. Thereafter, pJET-ARABW was cleaved with EcoRI and NdeI, and a DNA fragment containing araC and araB-W expression elements was recovered using a Gel- MTM gel extraction system kit (GMbiolab, Taiwan).
  • the araC and araB-W expression elements were ligated into pRPSJ-GFPT cut with the same restriction enzymes using T4 DNA ligase.
  • the bound product was transformed into E. coli ECOS 9-5.
  • the transformants were selected by colony polymerase chain reaction and plasmids were extracted for DNA sequencing confirmation.
  • the plasmid with the correct sequence was named pARABW-GFPT.
  • the AraCF primer was used together with the AraM1R, AraM2R, AraM3R, AraM4R, and AraM5R primers to modify the ribosome binding site sequence.
  • the 50 ⁇ L PCR reaction mixture contained 1 ⁇ GDP-HiFi PCR buffer B, 200 ⁇ M dATP, dTTP, dGTP and dCTP, 1 ⁇ M amplification primer, 100 ng ECOS 9-5 chromosome and 1 U GDP-HiFi DNA polymerase.
  • the PCR reaction conditions were 96 ° C for 5 minutes (1 step); 94 ° C for 30 seconds, 55 ° C for 30 seconds, 68 ° C for 1 minute (35 cycles); 68 ° C for 5 minutes (1 step).
  • the PCR product was recovered by PCR- MTM Clean Up system, bound to pJET1.2 plasmid by T4 DNA ligase, and the sequence was confirmed by DNA sequencing, and the plasmids were named pJET-ARABM1, pJET-ARABM2, respectively.
  • the five plasmids were cut with EcoRI and NdeI, respectively, and recovered with araC and araB-M1, araC and araB-M2, araC and araB-M3, araC using Gel-M TM gel extraction system kit (GMbiolab, Taiwan).
  • a DNA fragment with araB-M4, and araC and araB-M5 expression elements were ligated into pRPSJ-GFPT cleaved with the same restriction enzyme using T4 DNA ligase.
  • the bound product was transformed into E. coli ECOS 9-5.
  • the transformants were selected by colony polymerase chain reaction and plasmids were extracted for DNA sequencing confirmation.
  • the plasmids with the correct sequence were named pARABM1-GFPT, pARABM2-GFPT, pARABM3-GFPT, pARABM4-GFPT, and pARABM5-GFPT, respectively.
  • DNA fragment amplification was carried out using primer sets such as AraCF/AraM6-2 and AraM6-1/GFPSALIR, respectively.
  • primer sets such as AraCF/AraM6-2 and AraM6-1/GFPSALIR, respectively.
  • One-fold GDP-HiFi PCR buffer B, 200 ⁇ M dATP, dTTP, dGTP and dCTP, 1 ⁇ M amplification primer, 100 ng pARABM4-GFPT and 1 U GDP-HiFi DNA polymerase were included in the 50 ⁇ L PCR reaction mixture.
  • the conditions of the PCR reaction were 96 ° C for 2 minutes (1 step); 94 ° C for 30 seconds, 55 ° C for 30 seconds, 68 ° C for 1 minute (35 cycles); 68 ° C for 5 minutes (1 step).
  • agarose gel electrophoresis was used to confirm the presence or absence of a DNA fragment of an estimated size.
  • the PCR product was recovered using a Gel- MTM gel extraction system kit. Thereafter, DNA amplification was carried out using the AraCF/GFPSALIR primer combination using the recovered two PCR products as a template.
  • the conditions of the PCR reaction were 98 ° C for 2 minutes (1 step); 94 ° C for 30 seconds, 55 ° C for 30 seconds, 68 ° C for 1 minute (35 cycles); 68 ° C for 5 minutes (1 step). After this step, the araC and araB-M6 expression elements can be obtained.
  • the PCR product was recovered by PCR- MTM Clean Up system, bound to pJET1.2 plasmid by T4 DNA ligase, and the sequence was confirmed to be correct by DNA sequencing, and the plasmid was named pJET-ARABM6.
  • pJET-ARABM6 was cleaved with EcoRI and NdeI, and a DNA fragment containing araC and araB-M6 expression elements was recovered using a Gel- MTM gel extraction system kit.
  • the araC and araB-M6 expression elements were ligated into the same restriction enzyme cleavage pRPSJ-GFPT using T4 DNA ligase.
  • the bound product was transformed into E. coli ECOS 9-5.
  • the transformants were selected by colony polymerase chain reaction and plasmids were extracted for DNA sequencing confirmation.
  • the plasmid with the correct sequence was named pARABM6-GFPT.
  • DNA fragment amplification was carried out using primer sets such as AraCF/AraM7-2 and AraM7-1/GFPSALIR, respectively.
  • primer sets such as AraCF/AraM7-2 and AraM7-1/GFPSALIR, respectively.
  • One-fold GDP-HiFi PCR buffer B, 200 ⁇ M dATP, dTTP, dGTP and dCTP, 1 ⁇ M amplification primer, 100 ng pARABM4-GFPT and 1 U GDP-HiFi DNA polymerase were included in the 50 ⁇ L PCR reaction mixture.
  • the conditions of the PCR reaction were 96 ° C for 2 minutes (1 step); 94 ° C for 30 seconds, 55 ° C for 30 seconds, 68 ° C for 1 minute (35 cycles); 68 ° C for 5 minutes (1 step).
  • agarose gel electrophoresis was used to confirm the presence or absence of a DNA fragment of an estimated size.
  • the PCR product was recovered using a Gel- MTM gel extraction system kit. Thereafter, DNA amplification was carried out using the AraCF/GFPSALIR primer combination using the recovered two PCR products as a template.
  • the conditions of the PCR reaction were 96 ° C for 2 minutes (1 step); 94 ° C for 30 seconds, 55 ° C for 30 seconds, 68 ° C for 1 minute (35 cycles); 68 ° C for 5 minutes (1 step). After this step, the araC and araB-M7 expression elements can be obtained.
  • the PCR product was recovered by PCR- MTM Clean Up system, bound to pJET1.2 plasmid by T4 DNA ligase, and the sequence was confirmed to be correct by DNA sequencing, and the plasmid was named pJET-ARABM7.
  • pJET-ARABM7 was cleaved with EcoRI and NdeI, and a DNA fragment containing araC and araB-M7 expression elements was recovered using a Gel- MTM gel extraction system kit.
  • the araC and araB-M7 expression elements were ligated into the same restriction enzyme cleavage pRPSJ-GFPT using T4 DNA ligase.
  • the bound product was transformed into E. coli ECOS 9-5.
  • the transformants were selected by colony polymerase chain reaction and plasmids were extracted for DNA sequencing confirmation.
  • the plasmid with the correct sequence was named pARABM7-GFPT.
  • the AraCF primer was used together with the AraM10R primer to transform the expression element.
  • the 50 ⁇ L PCR reaction mixture contained 1 ⁇ GDP-HiFi PCR buffer B, 200 ⁇ M dATP, dTTP, dGTP and dCTP, 1 ⁇ M amplification primer, 100 ng ECOS 9-5 chromosome and 1 U GDP-HiFi DNA polymerase.
  • the PCR reaction conditions were 96 ° C for 5 minutes (1 step); 94 ° C for 30 seconds, 55 ° C for 30 seconds, 68 ° C for 1 minute (35 cycles); 68 ° C for 5 minutes (1 step).
  • the PCR product was recovered by PCR-MTM Clean Up system, bound to pJET1.2 plasmid by T4 DNA ligase, and the sequence was confirmed to be correct by DNA sequencing, and the plasmid was named pJET-ARABM10.
  • pJET-ARABM10 was cleaved with EcoRI and NdeI, and a DNA fragment containing araC and araB-M10 expression elements was recovered using a Gel- MTM gel extraction system kit.
  • the araC and araB-M10 expression elements were ligated into pRPSJ-GFPT cut with the same restriction enzymes using T4 DNA ligase.
  • the bound product was transformed into E. coli ECOS 9-5.
  • the transformants were selected by colony polymerase chain reaction and plasmids were extracted for DNA sequencing confirmation.
  • the plasmid with the correct sequence was named pARABM10-GFPT.
  • DNA fragment amplification was carried out using the AraCF/AraM10R primer set using pARABM7-GFPT as a template.
  • the 50 ⁇ L PCR reaction mixture contained 1 ⁇ GDP-HiFi PCR buffer B, 200 ⁇ M dATP, dTTP, dGTP and dCTP, 1 ⁇ M amplification primer, 100 ng pARABM7-GFPT and 1 U GDP-HiFi DNA polymerase.
  • the conditions of the PCR reaction were 96 ° C for 2 minutes (1 step); 94 ° C for 30 seconds, 55 ° C for 30 seconds, 68 ° C for 1 minute (35 cycles); 68 ° C for 5 minutes (1 step).
  • agarose gel electrophoresis was used to confirm the presence or absence of a DNA fragment of an estimated size.
  • the PCR product was recovered by Gel- MTM gel extraction system kit, and bound to pJET1.2 plasmid by T4 DNA ligase, and the sequence was confirmed to be correct by DNA sequencing, and the plasmid was named pJET-ARABM11. Thereafter, pJET-ARABM11 was cleaved with EcoRI and NdeI, and a DNA fragment containing araC and araB-M11 expression elements was recovered using a Gel- MTM gel extraction system kit.
  • the araC and araB-M11 expression elements were ligated into the same restriction enzyme cleavage pRPSJ-GFPT using T4 DNA ligase.
  • the bound product was transformed into E. coli ECOS 9-5.
  • the transformants were selected by colony polymerase chain reaction and plasmids were extracted for DNA sequencing confirmation.
  • the plasmid with the correct sequence was named pARABM11-GFPT.
  • Primers were designed for different downstream sequences and polymerase chain reaction was used for DNA amplification. DNA fragment amplification was carried out using different primer combinations using pARABM7-GFPT as a template.
  • the 50 ⁇ L PCR reaction mixture contained 1 ⁇ GDP-HiFi PCR buffer B, 200 ⁇ M dATP, dTTP, dGTP and dCTP, 1 ⁇ M amplification primer, 100 ng pARABM7-GFPT and 1 U GDP-HiFi DNA polymerase.
  • the conditions of the PCR reaction were 96 ° C for 2 minutes (1 step); 94 ° C for 30 seconds, 55 ° C for 30 seconds, 68 ° C for 30 seconds (35 cycles); 68 ° C for 5 minutes (1 step).
  • agarose gel electrophoresis was used to confirm the presence or absence of a DNA fragment of an estimated size.
  • Four PCR products were recovered by Gel- MTM gel extraction system kit and then cut with NdeI and SalI. After the restriction enzyme-cleaved PCR product was recovered by PCR-M TM Clean Up system, the above four DNA fragments containing the downstream sequence and the green fluorescent protein gene were inserted into pARABM7- which was cleaved by the same restriction enzyme using T4 DNA ligase. GFPT and pARABM11-GFPT. The bound product was transformed into E. coli ECOS 9-5. The transformants were selected by colony polymerase chain reaction and plasmids were extracted for DNA sequencing confirmation.
  • the plasmids with pARABM7-GFPT and the correct sequence were named pARABM7-DS1GFPT, pARABM7-DS2GFPT, pARABM7-DS4GFPT, and pARABM7-DS5GFPT, respectively, and the plasmids with pARABM11-GFPT and the correct sequence were named pARABM11- DS1GFPT, pARABM11-DS2GFPT, pARABM11-DS4GFPT, and pARABM11-DS5GFPT.
  • the arabinose-inducible expression vector obtained in Example 1 was transformed into Escherichia coli (ECOS 9-5), and protein (GFP) expression was induced.
  • the fluorescence intensity was measured by a microdisk analyzer to estimate the difference in expression levels between the expression element of Example 1 and the original expression element.
  • the Escherichia coli ECOS 9-5 transformant was inoculated into an LB medium containing tetracycline (25 ⁇ g/mL), and shake culture was carried out at 37 ° C and 180 rpm. After overnight incubation, the bacterial solution was inoculated to a LB medium containing tetracycline (25 ⁇ g/mL) at a ratio of 1:20. The shaking culture was carried out at 37 ° C and 180 rpm. The bacteria were cultured to measure the cell concentration by spectrophotometry to an OD 600 of about 0.4, and 0.2% arabinose was added for protein-induced expression.
  • the bacterial fraction was collected by centrifugation (20630 x g, 5 minutes, 4 °C), and the cells were washed with 1 mL of PBS buffer solution.
  • the bacterial fraction was collected by centrifugation (20630 x g, 5 minutes, 4 °C) and suspended in 1 mL of PBS buffer solution. 100 ⁇ L of the bacterial solution was taken out, and the absorbance of the bacterial liquid was measured at a wavelength of 600 nm using a TECAN INFINITE M200 microplate analyzer.
  • the fluorescence value of the sample was also measured at an excitation light wavelength of 482 nm and a radiation light wavelength of 512 nm.
  • the fluorescence intensity is expressed in terms of fluorescence per unit cell (fluorescence/OD 600 ). Please refer to Table 3 and Table 4 for the experimental results.
  • the araB-M1, araB-M2, araB-M3, araB-M4, and araB-M5 expression elements obtained by modifying the ribosome binding site were compared. It can be observed from the experimental data that all of the above five expression elements significantly increase the expression level of the gene to be expressed compared to the original expression element, wherein the expression level of the gene to be expressed using araB-M4 is the original 2.14 times the expression element.
  • the araB-M6 and araB-M7 expression elements and the original expression elements obtained by modifying the promoter-10 or the -16 site were compared. It can be observed from the data that the expression level of the gene to be expressed using araB-M6 was 3.42 times that of the original expression element, and that of araB-M7 was 2.87 times that of the original expression element. It is worth noting that the data for the araB-M6 and araB-M7 expression elements are 1.6 and 1.34 times that of araB-M4, respectively, meaning that the modification to the promoter-10 or the -16 site is directed to the ribosome binding site. The modification performed has an additive effect.

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Abstract

一种表达元件、表达盒，并以此建构出一种载体。该表达元件对于欲表达的基因的表达量有增进的效果，因而具有高度产业利用价值。

Description

表达元件、表达盒、及含其的载体 技术领域
本发明关于一种表达元件(expression Element)，尤指一种阿拉伯糖诱导表达系统的表达元件。
背景技术
表达系统(expression system)是由宿主细胞(host cell)与遗传元件(genetic element)如转录及转译讯号(transcription and translation signals)、调节因子(regulatory factor)、基因及质粒所组成。目前已有多种真核与原核表达系统被建立，甚至被商品化。
表达系统中，以大肠杆菌(Escherichia coli)表达系统的研究成果与开发经验最为丰硕，与此系统相关的基因操作技术与发酵技术发展得十分纯熟。以大肠杆菌生产重组蛋白质的优势包括基因操作简易、培养容易、生长快速且能于廉价的培养基中进行高密度(high density)培养、表达载体(expression vector)与改良宿主如蛋白酶缺损株(protease deficient strain)的选择性高、蛋白质产量高及生产时程短。
目前已有多种大肠杆菌表达系统可供使用，如trc表达系统、T7表达系统及pBAD表达系统等。其中，pBAD表达系统是一种阿拉伯糖诱导表达系统，由含有阿拉伯糖诱导表达元件与调控基因的表达载体搭配大肠杆菌宿主所构成，此表达系统优点为：(1)可紧密调控基因表达，避免某些基因的渗漏表达所造成的毒性；(2)以阿拉伯糖作为诱导剂的成本较为低廉；(3)可利用阿拉伯糖浓度调控蛋白质表达量。
鉴于阿拉伯糖诱导表达系统的上述优点，在研究及商业目的上都有开发更佳的表达元件的需求。
发明内容
爰是，本发明的一个目的在于提供表达元件及含其的表达盒(expression Cassette)，前述表达元件可提高欲表达的基因的表达量，因此更具产业利用价值。
本发明的另一个目的在于提供一种载体，其含有前述表达盒，且适用于阿拉伯糖诱导表达系统，因此可提供该领域于阿拉伯糖诱导表达系统的应用的新颖选择。
为了达到前述目的，本发明提供一种阿拉伯糖诱导表达系统的表达元件，其包含：启动子及至少一下列元件：
核糖体结合部位，其具有SEQ ID NO：01所示的序列；或
T7噬菌体转译增强元件，其具有SEQ ID NO：08所示的序列。
本发明又提供一种表达盒，其包含：前述表达元件、起始码、欲表达的基因、及终止码。
本发明另提供一种载体，其包含：前述表达盒及多重选殖部位。
较佳地，前述启动子的-10部位具有SEQ ID NO：06所示的序列。
较佳地，前述启动子的-16部位具有SEQ ID NO：07所示的序列。
较佳地，前述核糖体结合部位具有SEQ ID NO：02、SEQ ID NO：03、SEQ ID NO：04、SEQ ID NO：05、或其组合所示的序列。
较佳地，前述表达元件具有：SEQ ID NO：13、SEQ ID NO：14、SEQ ID NO：15、SEQ ID NO：16、SEQ ID NO：17、SEQ ID NO：18、SEQ ID NO：19、SEQ ID NO：20、SEQ ID NO：21、或其组合所示的序列。
较佳地，前述起始码与前述欲表达的基因之间设有下游序列；其中前述下游序列具有SEQ ID NO：09、SEQ ID NO：10、SEQ ID NO：11、SEQ ID NO：12、或其组合所示的序列。
较佳地，前述表达盒进一步包含调控基因。较佳地，前述调控基因为阿拉伯糖诱导表达调控基因araC。
较佳地，前述欲表达的基因为：转译为绿色荧光蛋白质的基因、酶基因、抗原基因、具生理活性的肽与蛋白质的基因、或其组合。
较佳地，前述载体进一步包含复制起始区域、筛选基因、信号肽、或其组合。
较佳地，前述载体所含筛选基因为：抗药性筛选基因、非抗药性筛选基因、或其组合。
综合以上所述，本发明提供一种阿拉伯糖诱导表达系统的表达元件及表达盒，以建构载体。前述载体通过大肠杆菌系统表达欲表达的蛋白质，且对于欲表达的基因有提高表达量的效能。据此，本发明提供一种表达载体作为基因工程领域中另一新颖的选择。
附图说明
图1显示比较本发明实施例中各表达元件的序列。
具体实施方式
有鉴于阿拉伯糖诱导表达系统于基因工程中的优点，本发明欲提供一种表达元件，其适用于阿拉伯糖诱导表达系统且有助于提高欲表达的基因的表达量。藉由使用本发明的表达元件，可使习用的阿拉伯糖表达系统更具产业价值。
本发明的一个面向是提供一种表达元件。前述表达元件包含启动子及至少一下列元件：核糖体结合部位或T7噬菌体转译增强元件。
本发明所述的「表达元件」是指起始码上游与基因表达有关的核苷酸序列。在一可行实施态样中，前述表达元件包含：启动子(含-10部位、-16部位、及/或-35部位)、核糖体结合部位、基因表达调控序列、或其组合。
在一可行实施态样中，前述启动子的种类无需限制，所属领域技术人员自可依其需求选用合适的启动子。在一较佳实施态样中，前述「启动子」为araB的启动子，而使得前述表达元件可适用于阿拉伯糖诱导表达系统中。在一个较佳实施态样中，前述启动子的-10部位具有SEQ ID NO：06所示的序列。在另一个较佳实施态样中，前述表达元件所含启动子的-16部位具有SEQ ID NO：07所示的序列。
本发明所述「核糖体结合部位」是指在转译过程中可为核糖体所辨识与结合的序列。在一个较佳实施态样中，前述核糖体结合部位具有SEQ ID NO：01。在一个可行实施态样中，前述核糖体结合部位具有SEQ ID NO：02、SEQ ID NO：03、SEQ ID NO：04、SEQ ID NO：05、或其组合所示的序列。本发明所称「T7噬菌体转译增强元件」为来自于噬菌体T7第十号基因起始码上游的核苷酸序列。于一可行实施态样中，前述T7噬菌体转译增强元件具有SEQ ID NO：08所示的序列。
本发明的又一个面向是提供一种表达盒，其包含前述表达元件、起始码、欲表达的基因、及终止码。在一个较佳实施态样中，前述起始码与前述欲表达的基因之间设有下游序列；其中前述下游序列具有SEQ ID NO：09、SEQ ID NO：10、SEQ ID NO：11、SEQ ID NO：12、或其组合所示的序列。在一个较佳实施态样中，前述表达盒进一步包含调控基因。
本发明所述的「调控基因」是指可转译出基因表达调控蛋白质的DNA序列。在 一可行实施态样中，前述调控基因为：araC。
本发明所述的「欲表达的基因」可依据使用者的需求不同而有所变动。前述欲表达基因例如，但不限于：转译绿色荧光蛋白质的基因、酶基因、抗原基因、具生理活性的肽与蛋白质的基因、或其组合。本发明所述的「起始码」是指mRNA中起始转译的密码子。在一可行实施态样中，前述起始码为：ATG。本发明所述的「终止码」是指终止转译的密码子。在一可行实施态样中，前述终止码为：TAA、TAG、或TGA。
本发明的另一个面向是提供一种载体，其包含前述表达盒及多重选殖部位。在一个较佳实施态样中，前述载体进一步包含复制起始区域、筛选基因、信号肽、或其组合。
在一可行实施态样中，前述多重选殖部位包含一种以上可为限制酶所辨识的核苷酸序列。前述限制酶包括但不限于：BamHI、BglII、EcoRI、HindIII、NdeI、PstI、SalI、SpeI、XbaI、XhoI、XmaI、或其组合。
本发明所称「筛选基因」是用来确认前述载体是否有顺利转化(transform)进入宿主体内。前述筛选基因可为但不限于：抗药性筛选基因、非抗药性筛选基因、或其组合。
本发明所称「抗药性筛选基因」是指以对抗生素的抗性确认载体的转化成功与否。举例来说，前述抗药性筛选基因为四环素抗性基因。在此可行实施态样中，顺利转化载体的宿主(如，大肠杆菌)便可以产生对四环素的抗性，而得以存活于含有四环素的环境。
本发明所称「非抗药性筛选基因」是指非以对抗生素的抗性与否来确认转化的基因。前述非抗药性筛选基因例如但不限于：β-半乳糖苷酶的核酸序列。在采用β-半乳糖苷酶的核酸序列作为筛选基因的实施态样中，转化成功的菌株会将X-gal(5-溴-4-氯-3-吲哚基-β-D-吡喃半乳糖苷)分解为半乳糖和5-溴-4-氯-3-羟基吲哚，而5-溴-4-氯-3-羟基吲哚会二聚合为5,5'-二溴-4,4'-二氯靛蓝，因此产生不可溶而可供辨识的蓝色物质。
在一较佳实施态样中，前述非抗药性筛选基因为营养缺损株的互补基因(如，胸苷酸合成酶基因、氨基酸合成相关基因、糖类合成相关基因及烟碱酰胺腺嘌呤二核苷酸合成相关基因)、脂肪酸合成基因fabI。
实施例一：本发明的阿拉伯糖诱导表达载体的建构与转化
本实施例是取得原始的阿拉伯糖诱导表达系统的表达元件，并分别对其中启动子-10部位、启动子-16部位、核糖体结合部位(Shine-Dalgarno sequence；SD)进行修 饰，或额外添加T7噬菌体转译增强序列(T7)及/或下游序列。再将前述表达元件与pRPSJ-GFPT、pARABM7-GFPT或pARABM11-GFPT接合，以构成本发明的表达载体。最后，以增强型绿荧光蛋白质基因作为报导基因，通过大肠杆菌表达系统表达欲表达的基因。本实施例中所制得的表达元件如下表1中所示：
表1：本实施例中所制得的表达元件
Figure PCTCN2014095340-appb-000001
本实施例的各式阿拉伯糖诱导表达载体建构过程如下：
1.原始阿拉伯糖诱导表达载体的建构
以大肠杆菌ECOS 9-5的染色体作为模板，利用AraCF及AraWR(GATATACATATGTTCACTCCATCCAAAAAAACGGGT；SEQ ID NO：46)引物组合进行原始阿拉伯糖诱导表达元件的扩增。在50μL聚合酶链式反应(polymerase chain reaction；PCR)混合物中包含1倍GDP-HiFi PCR缓冲液B，200μM的dATP、dTTP、dGTP与dCTP，1μM扩增引物，100ng ECOS 9-5的染色体及1U GDP-HiFi DNA聚合酶。PCR反应条件为96℃反应5分钟(1个步骤)；94℃反应30秒、55℃反应30秒、68℃反应1分钟(35个循环)；68℃反应5分钟(1个步骤)。将PCR产物以PCR-MTM Clean Up system回收，以T4 DNA连接酶黏合至pJET1.2质粒中，并利用DNA定序确认序列正确无误后，将质粒命名为pJET-ARABW。之后，以EcoRI与NdeI剪切pJET-ARABW，并利用Gel-MTM gel extraction system kit(GMbiolab,Taiwan)回收含有araC与araB-W表达元件的DNA片段。利用T4 DNA连接酶将araC与araB-W表达元件接入以相同限制酶剪切的pRPSJ-GFPT中。将黏合产物转化入大肠杆菌ECOS 9-5中。以菌落聚合酶链式反应挑选转化株并抽取质粒进行DNA定序确认。将序列正确无误的质粒命名为pARABW-GFPT。
2.核糖体结合部位经修饰的表达载体的建构
以大肠杆菌ECOS 9-5的染色体作为模板，利用AraCF引物搭配AraM1R、AraM2R、AraM3R、AraM4R、AraM5R引物进行核糖体结合部位序列的修饰。在50μL PCR反应混合物中包含1倍GDP-HiFi PCR缓冲液B，200μM的dATP、dTTP、dGTP与dCTP，1μM扩增引物，100ng ECOS 9-5的染色体及1U GDP-HiFi DNA聚合酶。PCR反应条件为96℃反应5分钟(1个步骤)；94℃反应30秒、55℃反应30秒、68℃反应1分钟(35个循环)；68℃反应5分钟(1个步骤)。将PCR产物以PCR-MTM Clean Up system回收，以T4 DNA连接酶黏合至pJET1.2质粒中，并利用DNA定序确认序列正确无误后，将质粒分别命名为pJET-ARABM1、pJET-ARABM2、pJET-ARABM3、pJET-ARABM4、及pJET-ARABM5，共5种。之后，以EcoRI与NdeI分别剪切此5种质粒，并利用Gel-MTM gel extraction system kit(GMbiolab,Taiwan)回收含有araC与araB-M1、araC与araB-M2、araC与araB-M3、araC与araB-M4、及araC与araB-M5表达元件的DNA片段。利用T4 DNA连接酶将前述 5种表达元件接入以相同限制酶剪切的pRPSJ-GFPT中。将黏合产物转化入大肠杆菌ECOS 9-5中。以菌落聚合酶链式反应挑选转化株并抽取质粒进行DNA定序确认。将序列正确无误的质粒分别命名为pARABM1-GFPT、pARABM2-GFPT、pARABM3-GFPT、pARABM4-GFPT、及pARABM5-GFPT。
3.启动子-10部位、及核糖体结合部位经修饰的表达载体的建构
以pARABM4-GFPT作为模版，利用AraCF/AraM6-2与AraM6-1/GFPSALIR等引物组分别进行DNA片段扩增。在50μL PCR反应混合物中包含1倍GDP-HiFi PCR缓冲液B，200μM的dATP、dTTP、dGTP与dCTP，1μM扩增引物，100ng pARABM4-GFPT及1U GDP-HiFi DNA聚合酶。PCR反应的条件为96℃反应2分钟(1个步骤)；94℃反应30秒、55℃反应30秒、68℃反应1分钟(35个循环)；68℃反应5分钟(1个步骤)。PCR反应结束后，利用琼脂糖胶体电泳确认有无预估大小的DNA片段。PCR产物以Gel-MTM gel extraction system kit回收。之后，以回收的两个PCR产物作为模版，利用AraCF/GFPSALIR引物组合进行DNA扩增。PCR反应的条件为98℃反应2分钟(1个步骤)；94℃反应30秒、55℃反应30秒、68℃反应1分钟(35个循环)；68℃反应5分钟(1个步骤)。经此步骤后，即可获得araC与araB-M6表达元件。将PCR产物以PCR-MTM Clean Up system回收，以T4 DNA连接酶黏合至pJET1.2质粒中，并利用DNA定序确认序列正确无误后，将质粒命名为pJET-ARABM6。之后，以EcoRI与NdeI剪切pJET-ARABM6，并利用Gel-MTM gel extraction system kit回收含有araC与araB-M6表达元件的DNA片段。利用T4 DNA连接酶将araC与araB-M6表达元件接入以相同限制酶剪切的pRPSJ-GFPT中。将黏合产物转化入大肠杆菌ECOS 9-5中。以菌落聚合酶链式反应挑选转化株并抽取质粒进行DNA定序确认。将序列正确无误的质粒命名为pARABM6-GFPT。
4.启动子-16部位、及核糖体结合部位经修饰的表达载体的建构
以pARABM4-GFPT作为模版，利用AraCF/AraM7-2与AraM7-1/GFPSALIR等引物组分别进行DNA片段扩增。在50μL PCR反应混合物中包含1倍GDP-HiFi PCR缓冲液B，200μM的dATP、dTTP、dGTP与dCTP，1μM扩增引物，100ng pARABM4-GFPT及1U GDP-HiFi DNA聚合酶。PCR反应的条件为96℃反应2分钟(1个步骤)；94℃反应30秒、55℃反应30秒、68℃反应1分钟(35个循环)；68℃ 反应5分钟(1个步骤)。PCR反应结束后，利用琼脂糖胶体电泳确认有无预估大小的DNA片段。PCR产物以Gel-MTM gel extraction system kit回收。之后，以回收的两个PCR产物作为模版，利用AraCF/GFPSALIR引物组合进行DNA扩增。PCR反应的条件为96℃反应2分钟(1个步骤)；94℃反应30秒、55℃反应30秒、68℃反应1分钟(35个循环)；68℃反应5分钟(1个步骤)。经此步骤后，即可获得araC与araB-M7表达元件。将PCR产物以PCR-MTM Clean Up system回收，以T4 DNA连接酶黏合至pJET1.2质粒中，并利用DNA定序确认序列正确无误后，将质粒命名为pJET-ARABM7。之后，以EcoRI与NdeI剪切pJET-ARABM7，并利用Gel-MTM gel extraction system kit回收含有araC与araB-M7表达元件的DNA片段。利用T4 DNA连接酶将araC与araB-M7表达元件接入以相同限制酶剪切的pRPSJ-GFPT中。将黏合产物转化入大肠杆菌ECOS 9-5中。以菌落聚合酶链式反应挑选转化株并抽取质粒进行DNA定序确认。将序列正确无误的质粒命名为pARABM7-GFPT。
5.核糖体结合部位、及T7噬菌体转译增强序列经修饰的表达载体的建构
以大肠杆菌ECOS 9-5的染色体作为模板，利用AraCF引物搭配AraM10R引物进行表达元件的改造。在50μL PCR反应混合物中包含1倍GDP-HiFi PCR缓冲液B，200μM的dATP、dTTP、dGTP与dCTP，1μM扩增引物，100ng ECOS 9-5的染色体及1U GDP-HiFi DNA聚合酶。PCR反应条件为96℃反应5分钟(1个步骤)；94℃反应30秒、55℃反应30秒、68℃反应1分钟(35个循环)；68℃反应5分钟(1个步骤)。将PCR产物以PCR-MTM Clean Up system回收，以T4 DNA连接酶黏合至pJET1.2质粒中，并利用DNA定序确认序列正确无误后，将质粒命名为pJET-ARABM10。之后，以EcoRI与NdeI剪切pJET-ARABM10，并利用Gel-MTM gel extraction system kit回收含有araC与araB-M10表达元件的DNA片段。利用T4 DNA连接酶将araC与araB-M10表达元件接入以相同限制酶剪切的pRPSJ-GFPT中。将黏合产物转化入大肠杆菌ECOS 9-5中。以菌落聚合酶链式反应挑选转化株并抽取质粒进行DNA定序确认。将序列正确无误的质粒命名为pARABM10-GFPT。
6.启动子-16部位、核糖体结合部位、及T7噬菌体转译增强序列经修饰的表达载体的建构
以pARABM7-GFPT作为模版，利用AraCF/AraM10R引物组进行DNA片段扩增。在50μL PCR反应混合物中包含1倍GDP-HiFi PCR缓冲液B，200μM的dATP、 dTTP、dGTP与dCTP，1μM扩增引物，100ng pARABM7-GFPT及1U GDP-HiFi DNA聚合酶。PCR反应的条件为96℃反应2分钟(1个步骤)；94℃反应30秒、55℃反应30秒、68℃反应1分钟(35个循环)；68℃反应5分钟(1个步骤)。PCR反应结束后，利用琼脂糖胶体电泳确认有无预估大小的DNA片段。PCR产物以Gel-MTM gel extraction system kit回收，以T4 DNA连接酶黏合至pJET1.2质粒中，并利用DNA定序确认序列正确无误后，将质粒命名为pJET-ARABM11。之后，以EcoRI与NdeI剪切pJET-ARABM11，并利用Gel-MTM gel extraction system kit回收含有araC与araB-M11表达元件的DNA片段。利用T4 DNA连接酶将araC与araB-M11表达元件接入以相同限制酶剪切的pRPSJ-GFPT中。将黏合产物转化入大肠杆菌ECOS 9-5中。以菌落聚合酶链式反应挑选转化株并抽取质粒进行DNA定序确认。将序列正确无误的质粒命名为pARABM11-GFPT。
7.添加下游序列的表达载体的建构
针对不同下游序列设计引物并利用聚合酶链式反应进行DNA的扩增。以pARABM7-GFPT作为模版，利用不同引物组合分别进行DNA片段扩增。在50μL PCR反应混合物中包含1倍GDP-HiFi PCR缓冲液B，200μM的dATP、dTTP、dGTP与dCTP，1μM扩增引物，100ng pARABM7-GFPT及1U GDP-HiFi DNA聚合酶。PCR反应的条件为96℃反应2分钟(1个步骤)；94℃反应30秒、55℃反应30秒、68℃反应30秒(35个循环)；68℃反应5分钟(1个步骤)。PCR反应结束后，利用琼脂糖胶体电泳确认有无预估大小的DNA片段。4种PCR产物以Gel-MTM gel extraction system kit回收后，以NdeI与SalI进行剪切。经限制酶剪切的PCR产物以PCR-MTM Clean Up system回收后，利用T4 DNA连接酶将前述4种含下游序列与绿荧光蛋白质基因的DNA片段接入以相同限制酶剪切的pARABM7-GFPT及pARABM11-GFPT中。将黏合产物转化入大肠杆菌ECOS 9-5中。以菌落聚合酶链式反应挑选转化株并抽取质粒进行DNA定序确认。将接入pARABM7-GFPT且序列正确无误的质粒分别命名为pARABM7-DS1GFPT、pARABM7-DS2GFPT、pARABM7-DS4GFPT、及pARABM7-DS5GFPT，而接入pARABM11-GFPT且序列正确无误的质粒则分别命名为pARABM11-DS1GFPT、pARABM11-DS2GFPT、pARABM11-DS4GFPT、及pARABM11-DS5GFPT。
前述实验流程中所用引物对如下表中所述。
表二：本发明所用引物对的序列与序列表的对照
Figure PCTCN2014095340-appb-000002
实施例二：本发明的阿拉伯糖诱导表达载体的分析
本实施例将实施例一所得的阿拉伯糖诱导表达载体转化进入大肠杆菌(ECOS 9-5)中，并诱导蛋白质(GFP)表达。接着，再以微盘分析仪测量荧光强度，以估算实施例一的表达元件与原始表达元件的表达量差异。
1.带有阿拉伯糖诱导表达载体的转化株进行诱导与荧光强度的测定
将大肠杆菌ECOS 9-5转化株接种于含四环素(25μg/mL)的LB培养基中，于37℃、180rpm的条件下进行振荡培养。经隔夜培养后，将菌液以1：20的比例接种至含有四环素(25μg/mL)的LB培养基中。于37℃、180rpm的条件下进行振荡培养。将细菌培养至以分光光度计量测细胞浓度达OD600约0.4，加入0.2％阿拉伯糖进行蛋白质诱导表达。诱导4小时后，离心(20630×g，5分钟，4℃)收集菌体部分，以1mL PBS缓冲溶液洗涤菌体。离心(20630×g，5分钟，4℃)收集菌体部分并悬 浮于1mL PBS缓冲溶液。取出100μL菌液，利用TECAN INFINITE M200微盘分析仪，在波长600nm下，测量菌液的吸光度，亦于激发光波长为482nm，放射光波长为512nm下，测定样品的荧光值。荧光强度(fluorescence intensity)以每单位细胞的荧光值(fluorescence/OD600)表示。实验结果请参表三及表四。
表三、原始表达元件与本发明的表达元件的表达效率
Figure PCTCN2014095340-appb-000003
表四、不同下游序列对表达效率的影响
Figure PCTCN2014095340-appb-000004
比较针对核糖体结合部位进行修饰所得的araB-M1、araB-M2、araB-M3、araB-M4、及araB-M5表达元件。从实验数据中可观察到所有前述5个表达元件相较于原始表达元件而论，皆显著地提升欲表达的基因的表达量，其中使用araB-M4的欲表达的基因的表达量是使用原始表达元件的2.14倍。
接着，比较针对启动子-10部位或-16部位进行修饰所得的araB-M6及araB-M7表达元件与原始表达元件。从数据中可观察到使用araB-M6的欲表达的基因的表达量是使用原始表达元件的3.42倍，而使用araB-M7者则为原始表达元件的2.87倍。值得注意的是，araB-M6及araB-M7表达元件的数据分别为araB-M4的1.6及1.34倍，意味着针对启动子-10部位或-16部位所进行的修饰与针对核糖体结合部位所进行的修饰有加成的效果。
比较加入T7噬菌体转译增强序列所得的araB-M10与araB-M4及原始表达元件，可观察到使用araB-M10者的表达量为araB-M4的1.07倍，且为原始表达元件的2.3倍。此外，比较加入T7噬菌体转译增强序列所得的araB-M11与araB-M7及原始表达元件，可观察到使用araB-M11者的表达量为araB-M7的1.08倍，且为原始表达元件的3.11倍。证实加入T7噬菌体转译增强序列对于表达量的正向效果。
根据表四，将araB-M7与araB-M11的起始码下游加入不同下游序列的8种表达元件与原始表达元件做比较，其中可观察到araB-M7-DS4的表达效率为araB-M7的1.04倍，且为原始表达元件的4.07倍。此外，其他表达元件和原始表达元件相较，表达效率也都有提升。

Claims (22)

  1. 一种表达元件，其包含：启动子及至少一下列元件：
    核糖体结合部位，其具有SEQ ID NO：01所示的序列；或
    T7噬菌体转译增强元件，其具有SEQ ID NO：08所示的序列。
  2. 如权利要求1所述的表达元件，其中前述启动子的-10部位具有SEQ ID NO：06所示的序列。
  3. 如权利要求1所述的表达元件，其中前述启动子的-16部位具有SEQ ID NO：07所示的序列。
  4. 如权利要求1所述的表达元件，其中前述核糖体结合部位具有SEQ ID NO：02、SEQ ID NO：03、SEQ ID NO：04、SEQ ID NO：05、或其组合所示的序列。
  5. 如权利要求1所述的表达元件，其具有：SEQ ID NO：13、SEQ ID NO：14、SEQ ID NO：15、SEQ ID NO：16、SEQ ID NO：17、SEQ ID NO：18、SEQ ID NO：19、SEQ ID NO：20、SEQ ID NO：21、或其组合所示的序列。
  6. 一种表达盒，其包含：如权利要求1所述的表达元件、起始码、欲表达的基因、及终止码。
  7. 如权利要求6所述的表达盒，其中前述表达元件中的启动子的-10部位具有SEQ ID NO：06所示的序列。
  8. 如权利要求6所述的表达盒，其中前述表达元件中的启动子的-16部位具有SEQ ID NO：07所示的序列。
  9. 如权利要求6所述的表达盒，其中前述表达元件中的核糖体结合部位具有SEQ ID NO：02、SEQ ID NO：03、SEQ ID NO：04、SEQ ID NO：05、或其组合所示的序列。
  10. 如权利要求6所述的表达盒，其中前述起始码与前述欲表达的基因之间设有下游序列；其中前述下游序列具有SEQ ID NO：09、SEQ ID NO：10、SEQ ID NO：11、SEQ ID NO：12、或其组合所示的序列。
  11. 如权利要求6所述的表达盒，其中前述表达元件具有：SEQ ID NO：13、SEQ ID NO：14、SEQ ID NO：15、SEQ ID NO：16、SEQ ID NO：17、SEQ ID NO：18、SEQ ID NO：19、SEQ ID NO：20、SEQ ID NO：21、或其组合所示的序列。
  12. 如权利要求6所述的表达盒，其进一步包含调控基因。
  13. 如权利要求12所述的表达盒，其中前述调控基因为阿拉伯糖诱导表达调控基因araC。
  14. 如权利要求6所述的表达盒，其中前述欲表达基因为：转译为绿色荧光蛋白质的基因、酶基因、抗原基因、具生理活性的肽与蛋白质的基因、或其组合。
  15. 一种载体，其包含：如权利要求6所述的表达盒、及多重选殖部位。
  16. 如权利要求15所述的载体，其中前述表达盒的表达元件中的启动子-10部位具有SEQ ID NO：06所示的序列。
  17. 如权利要求15所述的载体，其中前述表达盒的表达元件中的启动子-16部位具有SEQ ID NO：07所示的序列。
  18. 如权利要求15所述的载体，其中前述表达盒的表达元件中的核糖体结合部位具有SEQ ID NO：02、SEQ ID NO：03、SEQ ID NO：04、SEQ ID NO：05、或其组合所示的序列。
  19. 如权利要求15所述的载体，其中前述表达盒的前述起始码与前述欲表达的基因之间设有下游序列；其中前述下游序列具有SEQ ID NO：09、SEQ ID NO：10、SEQ ID NO：11、SEQ ID NO：12、或其组合所示的序列。
  20. 如权利要求15所述的载体，其中前述表达盒的表达元件具有：SEQ ID NO：13、SEQ ID NO：14、SEQ ID NO：15、SEQ ID NO：16、SEQ ID NO：17、SEQ ID NO：18、SEQ ID NO：19、SEQ ID NO：20、SEQ ID NO：21、或其组合所示的序列。
  21. 如权利要求15所述的载体，其进一步包含复制起始区域、筛选基因、信号肽、或其组合。
  22. 如权利要求21所述的载体，其中前述筛选基因为：抗药性筛选基因、非抗药性筛选基因、或其组合。
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