Herpes simplex virus thymidine kinase-green fluorescent protein fusion gene: new tool for gene transfer studies and gene therapy.

Green fluorescent protein (GFP) and herpes simplex virus type-I thymidine kinase (TK) are commonly used markers in gene transfer studies. The latter gene has also proven to be an effective tool in cancer "suicide" gene therapy. To facilitate rapid and reliable selection of cells expressing TK, we constructed a plasmid expressing a TK-green fluorescent protein fusion gene (TK-GFP). In this fusion gene, the expression of each component is coupled to one another, permitting accurate determination of the percentage of cells expressing TK by detecting the green fluorescence produced by GFP. Transfection of the fusion plasmid to mammalian cells revealed that the construct is fully functional, making the cells both fluorescent and sensitive to ganciclovir.