ABSTRACT
In this chapter, the authors aim to develop a rapid and efficient system for transfection and expression of foreign genes into the Drosophila Melanogaster S2 cell line. They describe a novel hygromycin B selection system which yields stable transformants within 3 weeks with no background of spontaneous resistant cells. Using the Escherichia coli gene for the galactokinase enzyme, the authors demonstrate the stable cotransfection of a nonselected gene at high copy number and the high level expression of its functional product. They compare the relative efficiencies of three promoters: the Drosophila COPIA 5'LTR, the Drosophila metallothionein (MT) promoter, and the mammalian viral SV40 early promoter. The MT promoter is tightly regulated by cadmium and other heavy metals and remains fully inducible even at high gene copy number. The authors also demonstrate the utility of the metallothionein promoter to regulate the expression of the human cH-ras gene and its oncogenic Val mutant who is toxic when overexpressed in S2 cells.
