Cell-specified expression of a selectable hybrid gene.

We have inserted into a retroviral vector the structural information encoding the selectable bacterial genes neo and gpt linked, respectively, to the promoters of the herpesvirus thymidine kinase gene and the rat preproinsulin II gene. We have used this recombinant retrovirus construction to transduce insulinoma cell lines that are positive or negative for insulin expression. Selection of the transductants for neo yielded resistant colonies from all of the cell lines, while selection for gpt yielded resistant transductants in relatively high frequency only from insulin-producing cells. The 5' end of the gpt transcripts maps to the authentic preproinsulin capping site of the construction.