FIG. 1.

Identification of the initiation codon on PTV Talfan RNA. (A) Genome organization of the PTV Talfan RNA. The presence of the virus-encoded peptide VPg (also called 3B), attached to the 5′ end of the genome, is depicted by a black square. The locations of potential initiation codons are indicated, and the sites of additional AUG codons that are out of frame with the polyprotein-coding sequence, are shown by arrowheads. The structures of plasmids which express, from the T7 promoter (black circles), portions of the PTV genome (within nt 1 to 1544) followed by sequences encoding a myc-epitope tag plus a termination codon (indicated by solid rectangles) are illustrated. (B) The indicated plasmids were used to program in vitro TNT reactions containing RRL and [³⁵S]-methionine. The products were analyzed by SDS-PAGE and autoradiography. (C) Plasmids expressing monocistronic transcripts were transfected into vTF7-3-infected BHK cells. After 20 h, cell lysates were prepared and analyzed by SDS-PAGE and immunoblotting using antibodies specific for the c-myc epitope tag (9E10). Products were detected with peroxidase-labeled antimouse antibodies and chemiluminescence reagents on X-ray film.