Transcription termination at T1-UP only occurs if ribosome translocation is prevented. (A,C) Schematic representation of model BUNV segments BUN-T697 and BUN-T936 and their derivatives. The T1-UP signal preceded by a UAA stop codon (shaded) was inserted at nucleotides 697 or 936 of the Renilla cDNA, such that the stop codon was in frame with the Renilla ORF (vertical lines). The two segments were modified by insertion or deletion of single nucleotides to position the UAA stop codon in alternative reading frames. (B,D) Direct analysis of RNAs synthesized by BUN-T697, BUN-T936, and their derivatives using agarose-urea gel electrophoresis. T1-UP signals were only active when translocation was blocked upstream.
