A dominant positive and negative selectable gene for use in mammalian cells.

We have constructed three different fusion genes containing the herpes simplex virus thymidine kinase (HSV tk) and the bacterial neomycin phosphotransferase (neo) genes. All three fusion genes utilize the HSV tk promoter but differ at the junction of their components. We have determined if the fusion genes are bifunctional by introducing them into mammalian cells and testing for function of the individual components. One of the fusion genes, TNFUS 69, produced a bicistronic message and a fusion protein that has TK and NEO protein functions. This and other fusion genes of a similar nature could serve as dominant positive and negative selectable markers in mammalian cells.