Examining the relative activity of several dicistrovirus intergenic internal ribosome entry site elements in uninfected insect and mammalian cell lines

Comparisons of the relative activities of 11 intergenic region (IGR) internal ribosome entry site (IRES) elements of insect dicistrovirus with 59′ IRES elements of the hepatitis C and encephalomyocarditis viruses were performed in insect and mammalian cells. Dual luciferase assays were performed to determine the most effective dicistrovirus IGR IRES in the lepidopteran cell lines Sf9 (Spodoptera frugiperda) and BmN (Bombyx mori), and the dipteran cell lines S2 (Drosophila melanogaster) and ATC-10 (Aedes aegypti). Evaluation of dual luciferase expression from DNA plasmids and in vitro-transcribed RNA revealed apparent splicing with certain IRES elements. Though IRES activity depended upon the cell line examined, the black queen cell and Drosophila C dicistrovirus intergenic IRES elements were most effective for coupled gene expression in the diverse insect cell lines examined.