FIG. 4.
Demonstration of NS2 gene deletion by RT-PCR. Total RNA of BSR T7/5 cells infected with standard BRSV ATue51908 or with recombinant virus was used for RT-PCR with a positive-sense primer hybridizing to the 3′ end of the BRSV genome RNA and a negative-sense primer binding in the N gene. Products from full-length recombinants and wild-type virus yielded a product of 1,179 bp (calculated size) spanning the NS2 gene, whereas deletion mutants gave rise to a 666-bp (calculated) fragment, reflecting the 513-nt deletion. No PCR product was detected when the RT step was omitted.