Predicted PRV transcript and gene organization. The linear form of the PRV genome is constituted of the larger unique long (UL) sequence to the left, and the smaller unique short (US) sequence flanked by the inverted repeats, IRS and TRS. The predicted locations of PRV ORFs (Table 3), 5′ and 3′ UTRs (Tables 4 and 6), DNA repeats (Table 5), splice sites (Fig. 1), and origin of replication are shown.