FIG 1.

Nucleotide substitutions in the phylogenetically conserved structural elements of the genomes of the poliovirus isolates in comparison with the Sabin 2 strain. The positions of changed nucleotides are represented by black dots, and the corresponding mutations are indicated; the nucleotides involved in the resulting base pairing (if formed) are also shown. (A) Domain II of the 5′ UTR. (B) Domains IV and V of the 5′ UTR. (C) Domain Y of the 3′ UTR. The structures are given as proposed previously (46, 48). (D) Possible tertiary (“kissing”) interaction between stem-loops 1 and 4 of the RNase L competitive inhibitor element of viral RNA (ciRNA) (47).