FIG. 4.

vhs induces cleavage downstream of an internally located EMCV IRES. (A) Uncapped, unlabeled transcripts of pCITE and pSexAI IRES were added to RRLs containing vhs (lanes marked vhs) and to control RRL (lanes marked RC), and samples were removed at the indicted times (in minutes). Following extraction, the reaction products were analyzed by primer extension, using a 5′-labeled oligonucleotide complementary to residues 1447 to 1471 of the pSexAI IRES RNA (and residues 1438 to 1462 of the pCITE transcript). Primer extension products were analyzed on an 8% polyacrylamide sequencing gel. Numbered arrows indicate primer extension products resulting from vhs-induced cleavage. (B) Diagram showing the nucleotide sequence at the 3′ boundary of the IRES in pSexAI IRES RNA. Numbered arrows correspond to those in panel A and indicate the locations of the novel 5′ ends produced by vhs-induced cleavage.