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The linear double-stranded genomes of poxviruses such as Shope fibroma virus (SFV) replicate autonomously within the cytoplasm of infected cells, and it is believed that all of the replication functions are virally encoded. During DNA replication the incompletely base-paired terminal hairpin loops of the viral genome transiently exist in the form of inverted repeat replicative intermediates. These inverted repeat structures form the target for telomere resolution events that include sequence-specific cleavage and directed strand exchange to form the hairpin termini of progeny virus genomes. The terminal sequence domain which forms the telomere resolution target (TRT) shares considerable sequence similarity with viral late promoters. In this study we demonstrate that the TRT of SFV is capable of functioning as a strong viral promoter late in infection. A spectrum of TRT mutations affects telomere resolution and late transcription in a strictly concordant fashion, suggesting that the two activities may be inextricably linked. Further support for this concept comes from the demonstration that a late SFV promoter sequence designated cryptic TRT, which differs substantially from the native TRT in terms of sequence, can support telomere resolution when placed in the correct spatial context. The proposed model for telomere resolution invokes directed unwinding of the TRT double helix by a transcription initiation complex and processing of the resulting secondary structure by viral late-gene products.


Journal article


Journal of virology

Publication Date





61 - 70


Department of Biochemistry, University of Alberta, Edmonton, Canada.


Cell Line, Animals, Poxviridae, Vaccinia virus, Restriction Mapping, Transfection, DNA Replication, Transcription, Genetic, Recombination, Genetic, Base Sequence, Repetitive Sequences, Nucleic Acid, Sequence Homology, Nucleic Acid, Genes, Viral, Molecular Sequence Data, Cottontail rabbit papillomavirus, Promoter Regions, Genetic