Encephalomyocarditis Virus Internal Ribosome Entry Site plasmid (EMCV IRES), for expressing two genes in mammalian cells under a CMV promoter.
Product Name: pSF-CMV-EMCV-PciI
Product Code: OG376
Size (bp): 4828 bp
Bacterial Antibiotic Selection: KanR
Origin and Compatibility: pUC high copy derived from pBR322
Bacterial Copy Number: 500-700 per cell
Promoter: Cytomegalovirus (CMV) immediate early promoter
This vector allows the expression of two genes from one vector. It contains the CMV promoter upstream of the primary multiple cloning site (MCS NotI-XbaI) followed by the internal ribosome entry site (IRES) from Encephalomyocarditis virus (EMCV) which is then followed by a secondary MCS. In this vector there is a PciI restriction site (which contains an ATG start codon) in the correct position to enable efficient expression of a gene from the IRES. This is the start codon that is preferentially used by ribosomes that engage onto the IRES to start translation.Promoter Expression Level:
This plasmid contains the mammalian CMV promoter to drive gene expression. We have tested all of our mammalian promoters in a range of cell types and CMV is consistently the strongest in those we have studied. However there are many reports of the CMV promoter demonstrating silencing by methylation in long-term culture. For this reason we stock a range of other promoters that are compatible with this plasmid and are available on request.
This plasmid contains three alternative transcription terminators for mammalian bacterial and bacteriophage (T7) expression. This means that only the promoter needs to be changed to alter the expression system you are using. We sell multiple promoters that can be used in each of these systems. The presence of each terminator does not reduce expression in the alternative systems.
There are a few important sites within the MCS. These include the NcoI site the XbaI site and the BsgI and BseRI sites. The NcoI site contains a start codon that is immediately downstream of both a Kozak and Shine-Dalgarno ribosomal binding site. These allow for optimal positioning of genes when the start codon is placed in this location. If this is not required and you wish to use a downstream site for gene cloning you can remove the NcoI site by cleaving the plasmid with KpnI.
The XbaI site contains a stop codon. This stop codon is positioned in a specific position in relation to the BsgI and BseRI sites that are immediately downstream. When either BseRI or BsgI cleave the plasmid they produce a TA overhang from the stop codon in the XbaI site that is compatible with all of our peptide tag plasmids cut with the same sites. BseRI and BsgI sites are non-palindromic and cleave a defined number of bases away from their binding site.
Whenever we clone a gene into our multiple cloning site we always position the start and stop codon in the same positions in the MCS. If the start and ends of the genes are not compatible with NcoI and XbaI we extend the sequence to the nearest external sites but keep the start and stop codons locations consistent.Cloning in a Gene into the upstream MCS:
This plasmid has been designed to be compatible with a range of cloning techniques. The multiple cloning site contains a range of standard commonly used restriction sites for cloning. Using these sites genes can be inserted using standard cloning methods with DNA ligase. Other methods such as ligase independent cloning (LIC) Gibson Assembly InFusionHD or Seamless GeneArt can also be used and because all of our plasmids are based on the same backbone the same method can be used for cloning into all of our catalogue vectors.