Insertion of Liver Enriched Transcription Factor Hepatocyte Nuclear Factor-4 (HNF-4) in a Vector which Contains Simian Virus (SV40) Promoter

One way of targeting gene expression in vivo is to control transcription using a tissue-specificregulatory system. Tissue-specific promoters or enhancers are in use in transgenic animals andcould be utilized in medicine for gene therapy. At present the usual method for selection of atissue-specific promoter is to identify a gene, which is expressed at unusually high level in thetarget tissue, and then to use the promoter for this gene to drive expression of another therapeuticgene in the target tissue. This approach is logical but does not always lead to high levels of geneexpression. A second approach is to investigate the scope for discovery of synthetic specificpromoters using a target tissue. The objective of the work described in this paper was to use bothapproaches to design plasmid DNA expression vectors that would carry liver-specific promoter /enhancer linked to a reporter gene (i.e. luciferase). Then transfect these vectors to both liver-derived and non-liver cell lines. This is followed by evaluation of the liver-specificity of each construct by measuring the basal level expression of the reporter gene (i.e. luciferase activity) in both cell lines.Hepatocyte nuclear factor-4 (HNF-4) is liver-enriched transcription factor used to design newsynthetic enhancers by inserting a tandem array of 1 , 3 or 5 repeats of the HNF-4 binding siteupstream of the SV40 promoter linked to the luciferase reporter gene within an Epstein-Barr virus (EBV)-based vector, p706. The results of transfection revealed that unexpectedly the HNF-4binding sites in these constructs act as a repressor rather than enhancer of the liver-specificexpression of the luciferase gene.