Figure 4.

The effect of downstream sequence on arrest at the 7/8 site. Templates were transcribed and size markers were generated from the NA2 template as described in Materials and Methods. In the lower part of the figure, sequences from the TH gene are underlined, distances downstream of +1 are given below the sequences and arrest positions are indicated by dots above the last nucleotide to be incorporated into the transcript. In the TsT template (containing the arrest site of the H3.3 gene), a 1 bp deletion occurred during cloning in the sequence upstream of the 50 bp inserted fragment, so transcripts of this template are 1 nt shorter than the numbers listed below the sequences (e.g. the sizes of the two major arrested transcripts are 73 and 74 nt).