FIG. 7.

Locus of a spontaneous mutation in the 3′-SL of D2/WN-SL(mutF) RNA associated with replication in monkey kidney cells and its effect on 3′-SL structure. Nucleotides are numbered from the 3′ terminus of the RNA genome, as in Fig. 1A and B. (A) Nucleotide sequence of the bottommost segment of the long stem in the 3′-SL of input D2/WN-SL(mutF) virion RNA, representing the substitution mutation introduced into D2/WN-SL(mutF) cDNA (see also Fig. 1A, 1B, and 2F). The substituted nucleotides were derived from the WN strain E101 nucleotide sequence (4) (Fig. 1B). Broad dashed lines indicate that the remainder of the 3′-SL nucleotide sequence is the same as that of wt DEN2 NGC RNA. Unpaired nt A₃ (shown in boldface) was deleted (dl A₃) in RNA isolated from D2/WN-SL(mutF) virus replicating in LLC-MK2 cells after transfection, as shown in panel B and as suggested by an arrow. (Note that the nucleotide numbering has been altered in panel B to reflect the deletion mutation.) (C) The analogous segment in the 3′-SL of wt DEN2 strain NGC virus RNA. Compared to the D2/WN-SL(mutF) nucleotide sequence, U₇₄ is replaced by C₇₄ (boldface) and the hydrogen-bonded U₇₆-A₄ base pair is replaced by unbonded U₇₆/U₄, forming a bulge in the long stem. (D) The nucleotide sequence of the analogous segment in the 3′-SL of an unspecified strain of WN virus, as determined by Wengler and Castle (33). The Wengler and Castle WN nucleotide sequence does not contain an unpaired A in the position analogous to that found in the Blackwell and Brinton nucleotide sequence. In panel D only, the fine dashed lines signify that the remainder of the 3′-SL nucleotide sequence is that of WN virus RNA, as determined by Wengler and Castle (data not shown).