C-box and G-box randomized libraries used in this study. (A) Schematic of the C-box and G-box elements in the four randomized viral libraries. Only the C-box and G-box regions of the unspliced genomic RNAs are represented. Nucleotide positions containing an “N” have an equal probability of being A, C, G, or U. The G-box mutation used in the forced selection is in bold lowercase letters. (B,C) Viral RNAs purified from the media fraction of transfected COS-7 cells were reverse-transcribed into cDNA. Primer extension of the different cDNA showed the degeneracy of the C-box randomized region in the C-box randomized viral library (B) and the G-box randomized region in the G-box randomized viral library (C).
