Comparison of several promoters and polyadenylation signals for use in heterologous gene expression in culturedDrosophilacells

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Abstract
We have directly compared the ability of four promoters and three polyadenylation (poly(A)) signals to direct heterologous gene expression In stably transfected Drosophila melanogaster S2 cells. We compared two constitutive Drosophila promoters, the actin 5C distal promoter and the α1-tubulin promoter, with the tightly regulated Drosophila metallothionein (Mtn) promoter and the Bombyx moii fibroin promoter. We find that the actln 5C and induced Mtn promoters generate comparable high levels of RNA and protein in this system. The a1-tubulin promoter generates about fourfold lower levels, and the fibroin promoter shows no detectable activity in S2 cells. Interestingly, genes expressed from the constitutive actin 5C and α1-tubulin promoters are consistently present at three- to four-fold lower copy numbers than genes expressed from the inducible Mtn promoter or the Inactive fibroin promoter. Poly(A) signals of both mammalian (SV40) and Drosophila (Mtn) origin efficiently directed stable RNA synthesis in S2 cells, and, as in mammalian cells, the SV40 late poly(A) signal was more efficient than the SV40 early poly(A) signal. Thus the process of polyadenylation appears to be conserved between mammalian and Drosophila cells.