Abstract:
A modified CAG promoter which is capable of driving high levels of expression of sequences of interest inserted downstream therefrom is herein described.

Description:
PRIOR APPLICATION INFORMATION 
     The instant application claims the benefit of U.S. Provisional patent application 61/086,948, filed Aug. 7, 2008. 
    
    
     BACKGROUND OF THE INVENTION 
     The Kozak consensus sequence or Kozak sequence plays a major role in the initiation of translation and has the consensus gcc(A/G)ccAUGG. 
     The CAG promoter comprises a hybrid CMV enhancer coupled to a modified chicken β-actin promoter. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the invention, there is provided a nucleotide sequence encoding a CAG promoter sequence as set forth in SEQ ID No. 1. 
     According to a second aspect of the invention, there is provided a nucleotide sequence comprising the CAG promoter sequence as set forth in SEQ ID No. 1 operably linked to a nucleic acid sequence comprising a Kozak sequence and a nucleic acid sequence encoding a codon-optimized Ebola virus glycoprotein as set forth in SEQ ID No. 2. 
     According to a third aspect of the invention, there is provided a purified or isolated functional promoter element having at least 70% or more identity with the nucleotide sequence as set forth in SEQ ID No. 1. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG.  1 ._pCAGalpha Sequence 
         FIG. 2 . Codon Optimized Ebola Glycoprotein Sequence 
         FIG. 3 . Bar graphs showing expression intensity of EGFP reporter gene in transfected HEK 293T cells as determined by FACS. Portions of the 5′ untranslated region of pCAGGS downstream of the CAG promoter were systematically removed generating pCAGGSΔ764-eGFP, pCAGGSΔ829-eGFP and pCAGGSΔ947-eGFP. Assays were performed in triplicate and repeated twice, the data shown is from one experiment. Error bars represent the standard deviation of the data. *p&lt;0.001. 
         FIG. 4  shows the construction of pCAGGSΔ829. The CAG promoter of the highly efficient expression plasmid pCAGGS is comprised of a CMV-IE enhancer coupled with a modified chicken-beta actin promoter. A minimal promoter sequence was identified following a deletion of 829 base pairs in the intron region using restriction enzyme Eco47III and XbaI, we termed this vector pcag-alpha. 
         FIG. 5  shows the construction of pCAGGSΔ764. The CAG promoter of the highly efficient expression plasmid pCAGGS is comprised of a CMV-IE enhancer coupled with a modified chicken-beta actin promoter. We deleted 764 base pairs in the intron region using restriction enzymes PspOMI and XbaI. The cohesive ends were filled in and ligated together using Klenow fragment and T4 DNA ligase. 
         FIG. 6  shows the construction of pCAGGSΔ947. The CAG promoter of the highly efficient expression plasmid pCAGGS is comprised of a CMV-IE enhancer coupled with a modified chicken-beta actin promoter. We deleted 947 base pairs in the intron region using restriction enzymes Eco47III and Acc65I. The cohesive ends were filled in and ligated together using Klenow fragment and T4 DNA ligase 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are now described. All publications mentioned hereunder are incorporated herein by reference. 
     Described herein is an expression cassette comprising an optimized CAG promoter sequence (SEQ ID No. 1), shown in  FIG. 1 . The promoter sequence was generated by deleting 829 base pairs using restriction enyzmes Eco47III and XbaI, filling the ends with Klenow and then religated the vector carrying the CAG promoter sequence with T4 Ligase, as shown in  FIG. 4 . As can be seen from  FIG. 3 , this deletion resulted in a promoter element having greater efficiency compared to a ‘wild type’ construct and other constructs containing a larger deletion. The construction of the ‘wild type’ element is described in Niwa et al., 1991, Gene 108:193-200, which is incorporated herein by reference in its entirety, particularly for the details on the construction of the expression vector). The details of the construction of the other plasmids are shown in  FIGS. 5 and 6 . Specifically,  FIG. 5  shows the construction of pCAGGSΔ764 in which 764 base pairs in the intron region were deleted using restriction enzymes PspOMI and XbaI.  FIG. 6  shows the construction of pCAGGSΔ947 in which 947 base pairs in the intron region were deleted using restriction enzymes Eco47III and Acc65I. In both cases, the cohesive ends were filled in and ligated together using Klenow fragment and T4 DNA ligase 
     As will be appreciated by one of skill in the art, such a promoter element can be used to drive high level expression of any gene of interest. 
     As will be appreciated by one skilled in the art,  FIG. 3  provides considerable information useful for the construction of similar promoter cassettes. Specifically, one of skill in the art having learned that an approximately 829 base pair deletion produces a promoter having increased expression whereas the 949 base pair deletion negates this increased expression can use this information together with methods known in the art to produce related promoter cassettes without undue experimentation. For example, one of skill in the art could easily construct a series of nested deletions using any of a variety of means known in the art such as for example methods allowing progressive deletion such as nuclease-based methods, restriction enzyme digests, sub-cloning and the like to delineate the exact location of the one or more ‘negative’ element(s) contained within the 829 base pair deletion fragment responsible for repression of transcriptional expression as well as the location of the one or more ‘positive’ element(s) located between the end-points of the 829 base pair deletion fragment and the 949 base pair deletion fragment. Furthermore, one of skill in the art could also easily envision other constructs for example constructs containing a deletion that would preserve the ‘phasing’ or relative orientation between the upstream promoter and the transcriptional start site and/or which contained slightly larger or somewhat smaller deletions but which still retained the promoter activity described herein. It is noted that the determination of the location of the positive element could of course be easily carried out using the construct described herein. It is accordingly held that constructs such as those described above which are functionally similar, function (that is, produce a similar but not necessarily identical level of expression, for example, a promoter cassette having 10%, 20%, 25%, 35% 45%, 50%, 55%, 65%, 75%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or more expression, preferably 50%, 55%, 65%, 75%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or more expression when compared to the promoter cassette described herein, wherein both constructs are transformed or transfected into the same or a similar cell line and expression is detected under similar conditions) to applicant&#39;s construct. 
     Also described is a nucleotide sequence comprising a Kozak sequence and a nucleotide sequence encoding an Ebola virus glycoprotein. Shown in  FIG. 2  is such a sequence wherein the codons encoding the Ebola virus glycoprotein have been selected so as to optimize translational efficiency of the Ebola virus glycoprotein in for example HEK 293T cells (SEQ ID No. 2). 
     In a preferred embodiment, the expression cassette comprises a nucleotide sequence encoding the CAG promoter sequence (SEQ ID No. 1) operably linked to a nucleic acid sequence comprising a Kozak sequence and a nucleic acid sequence encoding a codon-optimized Ebola virus glycoprotein (SEQ ID No. 2). 
     In a further embodiment of the invention, there is provided a purified or isolated functional promoter element having at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more identity with the nucleotide sequence as set forth in SEQ ID No. 1. It is of note that the promoter is considered to be ‘functional’ if the promoter has 10%, 20%, 25%, 35% 45%, 50%, 55%, 65%, 75%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or more expression, preferably 50%, 55%, 65%, 75%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or more expression when compared to the promoter cassette described herein as SEQ ID No. 1 when operably linked to a substantially identical reporter gene, transfected into a substantially similar cell line and grown under identical conditions, typically, conditions suitable for the expression of the report gene from the promoter, that is, expression driven by the promoter. 
     While the preferred embodiments of the invention have been described above, it will be recognized and understood that various modifications may be made therein, and the appended claims are intended to cover all such modifications which may fall within the spirit and scope of the invention.