Plasmids

pUC18

pUC18 and pUC19 vectors are small, high copy number, E.coli plasmids, 2686 bp in length. They are identical except that they contain multiple cloning sites (MCS) arranged in opposite orientations. pUC18/19 plasmids contain: (1) the pMB1 replicon rep responsible for the replication of plasmid (source – plasmid pBR322). The high copy number of pUC plasmids is a result of the lack of the rop gene and a single point mutation in rep of pMB1; (2) bla gene, coding for beta-lactamase that confers resistance to ampicillin (source – plasmid pBR322). It differs from that of pBR322 by two point mutations; (3) region of E.coli operon lac containing CAP protein binding site, promoter Plac, lac repressor binding site and 5’-terminal part of the lacZ gene encoding the N-terminal fragment of beta-galactosidase (source – M13mp18/19). This fragment, whose synthesis can be induced by IPTG, is capable of intra-allelic complementation with a defective form of beta-galactosidase encoded by host (mutation lacZDM15). In the presence of IPTG, bacteria synthesise both fragments of the enzyme and form blue colonies on media with X-gal. Insertion of DNA into the MCS located within the lacZ gene (codons 6-7 of lacZ are replaced by MCS) inactivates the N-terminal fragment of beta-galactosidase and abolishes alfa-complementation. Bacteria carrying recombinant plasmids therefore give rise to white colonies.

pCMV-b-gal

This is a high copy number eukaryotic vector, pCMVb expresses the full-length b-galactosidase gene under the control of the cytomegalovirus immediate early gene (CMV IE) promoter.  This vector is very useful for transfection of mammalian cells in culture and for use in other species.  The b-galactosidase enzyme expression is enhanced by elements including: SD/SA-RNA splice donor and acceptor sequence, and SV40 late polyadenylylation signal.  pCMVb expression vector also contains b-lactamase gene, which acts  as a selection marker (100mg/mL ampicillin resistance) in E. coli host.   pCMVb vector has been tested to generate up to 2530u/mg cell extract (MacGregor, and Caskey).  In addition, the b-galactosidase gene can be excised using the NotI sites to allow the insertion of other genes to be expressed under the same regulatory elements in mammalian cells.

pIRES2-EGFP

pIRES2-EGFP contains the internal ribosome entry site (IRES; 1, 2) of the encephalomyocarditis virus (ECMV) between the MCS and the enhanced green fluorescent protein (EGFP) coding region. This permits both the gene of interest (cloned into the MCS) and the EGFP gene to be translated from a single bicistronic mRNA. pIRES2-EGFP is designed for the efficient selection (by flow cytometry or other methods) of transiently transfected mammalian cells expressing EGFP and the protein of interest. This vector can also be used to express EGFP alone or to obtain stably transfected cell lines without time-consuming drug and clonal selection. EGFP is a red-shifted variant of wild-type GFP (3–5) which has been optimized for brighter fluorescence and higher expression in mammalian cells. The MCS in pIRES2-EGFP is between the immediate early promoter of cytomegalovirus (PCMV IE) and the IRES sequence. SV40 polyadenylation signals downstream of the EGFP gene direct proper processing of the 3' end of the bicistronic mRNA. The vector backbone also contains an SV40 origin for replication in mammalian cells expressing the SV40 T antigen. A neomycin-resistance cassette (Neor), consisting of the SV40 early promoter, the neomycin/kanamycin resistance gene of Tn5, and polyadenylation signals from the herpes simplex virus thymidine kinase (HSV TK) gene, allows stably transfected eukaryotic cells to be selected using G418. A bacterial promoter upstream of this cassette expresses kanamycin resistance in E. coli. The pIRES2-EGFP backbone also provides a pUC origin of replication for propagation in E. coli and an f1 origin for single-stranded DNA production.
pIRES2-EGFP replaces (but is not derived from) the pIRES-EGFP Vector previously sold by BD Biosciences Clontech. pIRES2-EGFP is functionally similarly to pIRES-EGFP; however, pIRES2- EGFP gives brighter EGFP fluorescence than the older vector.