FIG. 3.

Mapping of the initiation sites of four transcripts of the SIRV1 virus. The first (or only) ORF of the operon is indicated. Primer extension analysis was carried out using sequence-specific primers (see Materials and Methods). Each of the runoff products (PE) was electrophoresed alongside its DNA sequencing reactions (A, T, C, and G), also carried out with the corresponding primer. The promoter sequences are written in letters next to the autoradiographs. The TATA box, BRE, and GTC feature are highlighted in boxes.