Fig. 2.

Mutagenesis of PRRSV 3′ UTR. The upper panel shows the PRRSV genomic organization encoding 9 ORFs (denoted by boxed numbers), which is flanked by terminal untranslated regions (UTR) represented by gray bars. The lower panel depicts the 3′UTR mutations, in which restriction enzyme sites were inserted (Pac I and Asc I); Nucleotide deletion was engineered in p3URAD40 and p3URD40, respectively. In pSURLV, the entire 3′UTR of pAPRRS was replaced by that of type I PRRSV marked by the black-striped bar. “TGA” denotes the stop codon of the ORF7.