Journal of General Virology

Fig. 3. Model of misalignment mutagenesis to explain insertions and deletions in the genomic region preceding the second functional AUG in the mutant spectrum of C⁹₂₂ p50. Sequences and residue numbers are from Escarmís et al. (1996, 1999). +, Plus-strand, genomic RNA (the second functional AUG is boxed); –, negative-strand, antigenomic RNA. (A) Misalignment of the nascent minus-strand may lead to genomes with an increased number of adenylate residues (underlined). (B) Misalignment of the template plus-strand may lead to genomes with a decreased number of adenylate residues. (C) Realignment of the misaligned nascent minus-strand may lead to mutation G-1118A. (D) Misalignment of the template plus-strand, once uridine residues in the minus strand have been incorporated up to position 1119, may lead to deletion of G-1118. Note that this is an unlikely event, due to the necessity of the misalignment occurring when the minus strand has grown to a specific position, while in (A)–(C), a number of alternative misalignment events during minus-strand synthesis can lead to insertion of A, deletions or the G-1118A transition. The schemes are based on mechanisms proposed previously and reviewed by Ripley (1990).

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