FIG. 5.

Segregation of IRESs into three groups on the basis of length and sequence covariation of the pseudoknot and adjacent elements. The boundaries of elements in confirmed/putative picornavirus IRESs are as shown in Fig. 4B to H and references 1 and 54; the accession numbers for each genome are given in Materials and Methods. SPVs 1, 3, and 12 are identical to SPV-9, and SPVs 11 and 15 are identical to SPV-4 in the regions shown and were therefore excluded. All differences from consensus nucleotide sequences (“con.”) in panels A to C are indicated by a single-letter code; N indicates that there is no consensus. Vertical lines indicate Watson-Crick base pairing, and asterisks indicate GU base pairing.