Abstract:
A vector that allows for easy accomplishment of a variety of cloning, and use of the vector for measurement of the transcription-inducing activity of a promoter or production of a desired gene product in  Corynebacterium.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Korean Patent Application No. 10-2013-0008745, filed on 25 Jan. 2013, in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference. 
     INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ELECTRONICALLY 
     Incorporated by reference in its entirety herein is a computer-readable nucleotide/amino acid sequence listing submitted concurrently herewith and identified as follows: One 36,592 Bytes ASCII (Text) file named “713500_ST25.TXT,” created on Jan. 22, 2014. 
     BACKGROUND 
     1. Field 
     The present disclosure relates to shuttle vectors for  Corynebacterium  and  Escherichia coli , and promoter screening and gene product production using the same. 
     2. Description of the Related Art 
       Corynebacterium  is a gram-positive bacterial strain widely used for the production of amino acids, such as glutamate, lysine, and threonine, and purine based nucleic acids, such as inosinic acid.  Corynebacterium glutamicum , in particular, is easy to grow, tolerates high concentration cultivation (e.g., cultivation at concentrations up to approximately four times greater than concentrations tolerated by  Escherichia coli  ( E. coli )), and has a stable genome that resists mutations. In addition,  Corynebacterium glutamicum  has several merits as an industrial strain, such as being a nonpathogenic strain, not forming spores, thus having no deleterious effects on the environment, and the like. 
     A cloning vector is a cyclic DNA which can be replicated independently from a main chromosome in bacteria. A cloning vector includes an origin of replication for maintenance of a plasmid form within the strain, a selectable marker gene for selection of strains having the cloning vector, and a multi-cloning site (MCS) for cloning an exogenous gene. 
     A shuttle vector generally includes a vector which is capable of being maintained in a plurality of strains.  Corynebacterium - E. coli  shuttle vectors include both an origin of replication of  Corynebacterium  and an origin of replication of  E. coli . Use of shuttle vectors allows for easy introduction of a desired trait into a subject strain. For example, desired traits can be induced by cloning exogenous genes or mutation-inducing genes into a shuttle vector in  E. coli , and then introducing the shuttle vector into  Corynebacterium.    
     There is a need for shuttle vectors which are able to maintain and proliferate in both  Corynebacterium  and  E. coli , and which allow for easy accomplishment of a variety of cloning by improving a multi-cloning site. 
     SUMMARY 
     Provided are vectors including a nucleotide sequence of SEQ ID NO: 1 and a multi-cloning site (MCS) sequence of SEQ ID NO: 2. 
     Provided are methods of examining promoter activity in  Corynebacterium  using the vectors. 
     Provided are methods of producing gene products from  Corynebacterium  using the vectors. 
     Provided are  E. coli  and  Corynebacterium  having the vectors. 
     Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments. 
     According to an aspect of the present invention, a vector includes a nucleotide sequence of SEQ ID NO: 1 and a MCS sequence of SEQ ID NO: 2. For example, the vector may have a nucleotide sequence of SEQ ID NO: 3. The nucleotide sequence of SEQ ID NO: 3 refers to nucleotide sequence of the entire pGSK+ vector in  FIG. 2 . 
     The vector contain a reporter gene and a transcription terminator operably linked in the MCS (e.g., operably linked by or to the MCS, such that sequences inserted at the MCS are operably linked to the reporter gene and transcription terminator). The term “operably linked” means that one nucleic acid fragment is linked to another nucleic acid fragment and the function or expression of the former is affected by the latter. The reporter gene and the transcription terminator may be linked such that expression of the reporter gene can be regulated by a promoter inserted into the MCS. Any reporter gene that allows for easy measurement of transcription-inducing activity of the promoter may be used for the reporter gene. For example, the reporter gene may be a chloramphenicol acetyltransferase (CAT) gene. The transcription terminator may be, for example, an intrinsic transcription terminator. The intrinsic transcription terminator may be, for example, a rrnB terminator. The vector may have, for example, a nucleotide sequence of SEQ ID NO: 4. The nucleotide sequence of SEQ ID NO: 4 refers to nucleotide sequence of the entire pGSP1 vector in  FIG. 3 . 
     The vector may be one in which a 3′-untranslated region (3′UTR) inducing gene expression stabilization, and a transcription terminator are operably linked in the MCS. The 3′UTR and the transcription terminator may be linked such that a gene of a promoter-gene inserted into the MCS can be stably expressed. The 3′UTR may be, for example, the 3′UTR of the  Corynebacterium  gltA gene. The transcription terminator may be, for example, an intrinsic transcription terminator. The intrinsic transcription terminator may be, for example, a rrnB terminator. The vector may have, for example, a nucleotide sequence of SEQ ID NO: 5. The nucleotide sequence of SEQ ID NO: 5 refers to nucleotide sequence of the entire pGT1 vector in  FIG. 4 . 
     The vector may contain a constitutive promoter, a 3′-untranslated region inducing gene expression stabilization, and a transcription terminator operably linked in the MCS. The “constitutive promoter” includes a promoter having a certain level of transcriptional activity regardless of growth conditions. The constitutive promoter may be, for example,  Corynebacterium glutamicum -derived glyceraldehyde-3-phosphate dehydrogenase (gapA) (NCg11526) gene promoter. The constitutive promoter may be, for example, one which is linked to a gene so that the gene inserted into the MCS can be expressed at a certain level regardless of the growth conditions of  Corynebacterium . The 3′UTR and the transcription terminator may be, for example, linked such that the gene inserted into the MCS can be expressed. The 3′UTR may be, for example, the 3′UTR of the  Corynebacterium  citrate synthase (gItA) gene. The transcription terminator may be, for example, an intrinsic transcription terminator. The intrinsic transcription terminator may be, for example, a rrnB terminator. The vector may have, for example, the nucleotide sequence of SEQ ID NO: 6. The nucleotide sequence of SEQ ID NO: 6 refers to nucleotide sequence of the entire pGSX1 vector in  FIG. 5 . 
     According to another aspect of the present invention, a method of examining promoter activity includes: culturing a vector-introduced  Corynebacterium  in a medium, wherein the vector includes a nucleotide sequence of SEQ ID NO: 1 and a MCS sequence of SEQ ID NO: 2, and contains a reporter gene and a transcription terminator operably linked in the MCS, wherein a promoter is inserted into the MCS; measuring a product of the reporter gene; and examining the transcription-inducing activity of the promoter. 
     The culturing may be performed in any medium in which  Corynebacterium  can grow and proliferate. The promoter may be inserted into the MCS such that the reporter gene, which is operably linked to the promoter, is expressed. The promoter may be, for example, a promoter for testing the transcription-inducing activity in  Corynebacterium . The transcription terminator may be, for example, an intrinsic transcription terminator. The intrinsic transcription terminator may be, for example, a rrnB terminator. The  Corynebacterium  may be, for example,  Corynebacterium glutamicum . The reporter gene product may be, for example, chloramphenicol acetyltransferase. 
     For measuring the reporter gene product, a cytolysate of  Corynebacterium  may be obtained. Measuring the reporter gene product may be carried out, for example, by incubating the cytolysate of  Corynebacterium  containing a vector of the present invention, radioisotope-labelled chloramphenicol, and acetyl-CoA at 37° C. to produce radioisotope-labelled acetylchloramphenicol, and examining the radioisotope-labelled acetylchloramphenicol by chromatography and/or radioautography. The measuring also may be carried out by measuring the size of colonies formed on a chloramphenicol-containing medium. 
     The examining of transcription-inducing activity may be carried out, for example, by measuring acetylchloramphenicol produced, as compared to a control group. In this regard, the control group may be  Corynebacterium  containing a vector lacking a promoter insert cultured under identical conditions. The examining of transcription-inducing activity also may be carried out by examining whether larger colonies are formed or not, as compared to the control group. In this regard, the control group may be  Corynebacterium  containing a vector lacking a promoter insert cultured on a chloramphenicol-containing medium. 
     According to another aspect of the present invention, a method of producing a gene product from  Corynebacterium  includes: culturing a vector-introduced  Corynebacterium  in a medium, wherein the vector includes a nucleotide sequence of SEQ ID NO: 1 and a MCS sequence of SEQ ID NO: 2, and in which a constitutive promoter, a 3′UTR, and a transcription terminator are operably linked in the MCS, and in which a gene is inserted into the MCS; and separating a product of the gene from a result of the culturing. 
     The culturing may be performed in any medium in which  Corynebacterium  can grow and proliferate. The gene may be, for example, a gene for testing whether a gene product is produced in  Corynebacterium . The gene may be, for example, one which is inserted into the MCS such that the expression of the gene is induced by the constitutive promoter. The constitutive promoter may be, for example, a  Corynebacterium glutamicum -derived gapA gene promoter. The 3′UTR may be, for example, a 3′UTR of the  Corynebacterium  gltA gene. The transcription terminator may be, for example, an intrinsic transcription terminator. The intrinsic transcription terminator may be, for example, a rrnB terminator. The  Corynebacterium  may be, for example,  Corynebacterium glutamicum.    
     The separating of a gene product may be carried out, for example, by harvesting a cultured cell, lysing the cell, and separating proteins from an obtained cell extract using common methods, such as chromatography, electrophoresis, etc. The separated gene product may undergo, for example, an additional purification process. 
     According to another aspect of the present invention,  E. coli  has a vector which includes the nucleotide sequence of SEQ ID NO: 1 and the MCS sequence of SEQ ID NO: 2. The  E. coli  may contain, for example, the nucleotide sequence of SEQ ID NO: 3. The  E. coli  may contain, for example, a vector which includes the nucleotide sequence of SEQ ID NO: 1 and the MCS sequence of SEQ ID NO: 2, wherein a reporter gene and a transcription terminator are operably linked in the MCS. The reporter gene and the transcription terminator may be, for example, linked such that the expression of the reporter gene can be regulated by a promoter inserted into the MCS. The reporter gene may be, for example, a chloramphenicol acetyltransferase gene. The  E. coli  may contain, for example, a vector which has the nucleotide sequence of SEQ ID NO: 4. 
     The  E. coli  may contain, for example, a vector which includes the nucleotide sequence of SEQ ID NO: 1 and the MCS sequence of SEQ ID NO: 2, wherein a 3′UTR and a transcription terminator are operably linked in the MCS. The 3′UTR and the transcription terminator are as described above. The 3′UTR and the transcription terminator may be, for example, linked such that the gene of the promoter-gene inserted into the MCS can be expressed. The  E. coli  may contain, for example, a vector which has the nucleotide sequence of SEQ ID NO: 5. 
     The  E. coli  may be used, for example, as a host cell for maintaining and proliferating the vector. A group of the host cells may constitute a genomic DNA library. The vector may include, for example, each fragment of the  Corynebacterium glutamicum  genome. 
     The  E. coli  may contain, for example, a vector which includes the nucleotide sequence of SEQ ID NO: 1 and the MCS sequence of SEQ ID NO: 2, wherein a constitutive promoter, a 3′UTR, and a transcription terminator are operably linked in the MCS. The constitutive promoter, the 3′UTR, and the transcription terminator are as described above. The constitutive promoter may be, for example, linked to the gene so that the gene inserted into the MCS can be expressed at a certain level regardless of the growth conditions of  Corynebacterium . The 3′UTR and the transcription terminator may be, for example, linked such that the gene inserted into the MCS can be expressed. The  E. coli  may contain, for example, a vector which has the nucleotide sequence of SEQ ID NO: 6. 
     According to another aspect of the present invention,  Corynebacterium  has a vector which includes a nucleotide sequence of SEQ ID NO: 1 and a MCS sequence of SEQ ID NO: 2. The  Corynebacterium  may contain, for example, a nucleotide sequence of SEQ ID NO: 3. 
     The  Corynebacterium  may contain, for example, a vector which includes the nucleotide sequence of SEQ ID NO: 1 and the MCS sequence of SEQ ID NO: 2, wherein a reporter gene and a transcription terminator are operably linked in the MCS. The reporter gene and the transcription terminator may be, for example, linked such that expression of the reporter gene can be regulated by a promoter inserted into the MCS. The reporter gene may be, for example, chloramphenicol acetyltransferase gene. The  Corynebacterium  may contain, for example, a vector which has a nucleotide sequence of SEQ ID NO: 4. 
     The  Corynebacterium  may contain, for example, a vector which includes the nucleotide sequence of SEQ ID NO: 1 and the MCS sequence of SEQ ID NO: 2, wherein a 3′UTR and a transcription terminator are operably linked in the MCS. The 3′UTR and the transcription terminator are as described above. The 3′UTR and the transcription terminator may be, for example, linked such that a gene of a promoter-gene inserted into the MCS can be expressed. The  Corynebacterium  may contain, for example, a vector which has a nucleotide sequence of SEQ ID NO: 5. 
     The  Corynebacterium  may contain, for example, a vector which includes the nucleotide sequence of SEQ ID NO: 1 and the MCS sequence of SEQ ID NO: 2, wherein a constitutive promoter, a 3′UTR, and a transcription terminator are operably linked in the MCS. The constitutive promoter, the 3′UTR, and the transcription terminator are as described above. The constitutive promoter may be, for example, linked to a gene so that the gene inserted into the MCS can be expressed at a certain level regardless of the growth conditions of  Corynebacterium . The 3′UTR and the transcription terminator may be, for example, linked such that the gene inserted into the MCS can be expressed. The  Corynebacterium  may contain, for example, a vector which has a nucleotide sequence of SEQ ID NO: 6. The  Corynebacterium  may be used, for example, as a host cell which overexpresses the gene inserted in the vector. 
     The  Corynebacterium  may be, for example,  Corynebacterium glutamicum.    
     According to one embodiment, the shuttle vector of the present invention can be used for gene cloning, gene or promoter screening, gene product production, and genomic DNA library manufacture in  Corynebacterium.    
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a map, photographs, and a gel image showing that four pET2 mini vectors manufactured by serial deletion are maintained and replicated in  Corynebacterium glutamicum;    
         FIG. 2  is a map of pGSK+, a shuttle vector for gene cloning; 
         FIG. 3  is a map of pGPS1, a shuttle vector for promoter screening; 
         FIG. 4  is a map of pGT1, a shuttle vector for promoter-gene cloning; and 
         FIG. 5  is a map of pGSX1, a shuttle vector for exogenous gene overexpression. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the present embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain aspects of the present description. 
     Example 1 
     Manufacture of pET2 Mini Vector through Serial Deletion 
     A mini vector made up of the site represented by A (pET2 mini A, 4911 bp), a mini vector made up of the site represented by B (pET2 mini B, 4818 bp), a mini vector made up of the site represented by C (pET2 mini C, 4717 bp), and a mini vector made up of the site represented by D (pET2 mini D, 4647 bp) were manufactured from a  E. coli - Corynebacterium glutamicum  shuttle vector, pET2 (GenBank accession number: AJ885178.1, 7513 bp). 
       FIG. 1  is an experimental result showing that four pET2 mini vectors manufactured by serial deletion are maintained and replicated in  Corynebacterium glutamicum .  FIG. 1(A)  shows a site of independent mini vectors manufactured from pET2 vector.  FIG. 1(B)  shows that when pET2 mini D, whose size was reduced by about 270 bp as compared to pET2 mini A, was transformed in  Corynebacterium glutamicum , a larger number of colonies were obtained.  FIG. 1(C)  shows a result confirming that each mini vector was maintained in a form of plasmid in both  E. coli  and  Corynebacterium glutamicum . Lane E confirms that the plasmid was separated from  E. coli . Lanes 1 to 3 confirm that the plasmids were separated from  Corynebacterium glutamicum.    
     Example 2 
     pGSK+, Shuttle Vector for Cloning  E. coli - Corynebacterium qlutamicum    
     Based on pET2 mini D in Example 1, a pET2-derived kanamycin-resistance gene, aph gene, was substituted with a Tn5-derived kanamycin-resistance gene, neo gene (nptII), to remove a restriction enzyme recognition site. In addition, an XbaI restriction enzyme recognition site in the rep gene was removed by point mutation. Then, the MCS derived from pBluescriptII SK(+) phagemid vector, which has 14 restriction enzyme recognition sites, was inserted to manufacture a shuttle vector for cloning  E. coli - Corynebacterium glutamicum , pGSK+. 
       FIG. 2  shows a map of pGSK+, the shuttle vector for gene cloning. It shows a genetic organization along with restriction enzyme recognition sites. Arrows refer to open reading frames (ORFs) and the directions of arrows refer to the direction of transcription. pMB1 on refers to a replication origin for replication in  E. coli , and pBL1 cgl on refers to a replication origin for replication in  Corynebacterium glutamicum , and its portion, rep, refers to a CgI replicase gene. 
     Example 3 
     pGPS1, Shuttle Vector for Promoter Screening 
     Based on pGSK+ in Example 2, a pET2-derived chloramphenicol acetyltransferase (CAT) gene-rrnB terminator was inserted between ClaI and SacI in a MCS to manufacture a shuttle vector for promoter screening, pGPS1. 
       FIG. 3  shows a map of pGPS1, the shuttle vector for promoter screening. It shows a genetic organization along with restriction enzyme recognition sites. Arrows refer to ORFs and the directions of arrows refer to the direction of transcription. pMB1 ori, pBL1 CgI ori, and rep are as described in Example 2. cat refers to the chloramphenicol acetyltransferase gene, and rrnBT refers to a rrnB terminator. 
     Example 4 
     pGT1, Shuttle Vector for Promoter-exogenous Gene Cloning 
     Based on pGSK+ in Example 2, the 3′UTR (untranslated region) of the gltA gene and rrnB terminator were inserted into the SalI position of pGSK+ to manufacture a shuttle vector for promoter-exogenous gene cloning, pGT1. 
       FIG. 4  shows a map of pGT1, the shuttle vector for promoter-gene cloning. It shows a genetic organization along with restriction enzyme recognition sites. Arrows refer to ORFs and the directions of arrows refer to the direction of transcription. pMB1 ori, pBL1 CgI ori, rep, and cat are as described in Example 2 and Example 3. 
     Example 5 
     pGSX1, Shuttle Vector for Overexpression 
     Based on pGT1 in Example 4, a promoter of  Corynebacterium glutamicum -derived gapA gene was inserted between KpnI and XhoI in the MCS to manufacture a shuttle vector for exogenous gene overexpression, pGSX1. 
       FIG. 5  shows a map of pGSX1, the shuttle vector for exogenous gene overexpression. It shows a genetic organization along with restriction enzyme recognition sites. Arrows refer to ORFs and the directions of arrows refer to the direction of transcription. pMB1 ori, pBL1 CgI ori, rep, and cat are as described in Example 2 and Example 3. PgapA refers to the promoter of a gapA gene. 
     It should be understood that the exemplary embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments.