The 32 P-labeled or unlabeled full-length DI-72 (+) and (2)RNAs and the four separate regions (RI-IV), were generated as described [57] . Transcripts for replicase or CFE replication assays were purified as described earlier [57] . The amounts of transcripts were quantified by UV spectrophotometer (Beckman). To obtain fulllength FHV-derived DI-634 RNA [72] , we used primers #3842 (GTAATACGACTCACTATAGTAAACAATTCCAAGTTCC-AAAATGG) and #3509 (ACCTTAGTCTGTTGACTTAAA-CTGG) or #3519 (GTAAACAATTCCAAGTTCC) and #3527 (GTAATACGACTCACTATAGGGAACCTTAGTCTGTTG-ACTTAAAC) for (+) or (2)DI-634 RNAs, respectively, and pDI634 [72] as a template in PCR reactions. The RNA transcripts were synthesized on the PCR templates using T7based transcription [47] .