FIG. 7.

The NS1 protein inhibits the synthesis of positive-sense RNA from the minigenome MP13. MP13 is an analog of genomic RNA that encodes two short mRNAs from the upstream and downstream ends of the CAT ORF (mRNAs 1 and 2, which are 271 and 495 nt exclusive of poly[A]), as illustrated in Fig. 1. In addition, MP13 is restricted from amplification by the RSV polymerase due to a point mutation (TrG5A) in the trailer region. (A) 293 cells were infected with vTF7-3 and transfected with MP13 minigenome and the N, P, and L support plasmids in the same amounts as in Fig. 3 and the indicated amount (0 to 50 ng) of NS1 plasmid. L plasmid was omitted from lane 1 as a negative control. RNA was isolated 40 h postinfection and analyzed by Northern blot hybridization with negative-sense RSV-CAT riboprobe. (B) The hybridized radioactivity was quantitated on a PhosphorImager (B). Each RNA species was normalized separately with respect to the sample that received L, N, P, but no NS1 (lane 2) as 100%.