FIG. 4.
Effect of gene end U tract length and the first intergenic nucleotide on transcriptional termination. (A) Sequence of the M/SH gene junction aligned with the sequence from replicons having shortened U tracts and variation in the first intergenic nucleotide. The U tracts are underlined, and the first intergenic nucleotide is in bold. (B) RNA synthesized from wild-type M/SH junction compared to that from altered M/SH junctions. HEp-2 cells, infected with MVA-T7, were transfected with pM/SH-B or one of the mutant replicons along with the HRSV support plasmids pN, pP, pM2ORF1, and L1049D or L1049N. RNAs were labeled and visualized as described for Fig. 2B. Quantitation of percent termination efficiency (TE) was calculated by densitometric analysis of fluorographs from three experiments and is shown below each lane.