Proposed RNA secondary structure of the BVDV (strain SD-1) 5' UTR. The map was adapted from computer-predicted structures published by Deng and Brock . The domain denomination by Deng and Brock makes use of uppercase letters. The nomenclature used in Brown et al. is indicated by roman numbers . Two out of the seven AUGs in the BVDV leader are shown, the AUG used for initiation of translation is boxed. The putative RNA pseudoknot interaction is depicted by dashed lines. Arrows indicate the position of restriction enzymes used to construct the deletion mutants.