Introduction of Dicistrovirus IRESs into UAS/SV40-polyA constructs results in premature polyadenylation and strong overexpression of the upstream ORF in Drosophila animals

To evaluate the properties of insect virus internal ribosomal entry sites (IRESs) for protein expression in Drosophila, we have introduced Cricket Paralysis virus (CrPV) and Drosophila C virus (DCV) IRESs into UAS/SV40-polyA vector. We found that introduction of IRESs induce premature polyadenylation, resulting in both truncation of the mRNA, and an increase in mRNA levels of approximately 40-fold. The increase in mRNA levels was accompanied by increased resistance to nonsense-mediated mRNA decay (NMD)-mediated degradation. Our results suggest that premature polyadenylation increases mRNA stability in the SV40 polyadenylation site-containing constructs, suggesting a novel method for robust overexpression of transgenes in Drosophila.