Incompletely base-paired flip-flop terminal loops link the two DNA strands of the vaccinia virus genome into one uninterrupted polynucleotide chain

Telomeres of the linear chromosomes of Lyme disease spirochaetes: nucleotide sequence and possible exchange with linear plasmid telomeres

“…No inviolate correlations could be made among the chromosome length at the right telomere, the presence of chromosomal right-end-like sequences on linear plasmids, the biological source of the isolates (tick or vertebrate host), or the geographic site of isolation (Table 3). However, a disproportionately high number of vertebrate isolates (9 out of 12; 75%) ᮊ 1997 Blackwell Science Ltd, Molecular Microbiology, 26, 581-596 burgdorferi Sh-2-82 above; right end of B. afzelii R-IP3 below; sequence determined in this report), the bacteriophage N15 prophage plasmid (Svarchevsky and Rybchin, 1984;Malinin et al, 1992), African swine fever virus (González et al, 1986), vaccinia virus (Baroudy et al, 1982), and one end of the Paramicium mitochondrial DNA (Pritchard and Cummings, 1981) are shown. Note that the two telomeres of the poxvirus (vaccinia) and iridopoxvirus (African swine fever) chromosomes contain unpaired bases.…”

“…In theory this difficulty can be overcome in several ways (Cavalier-Smith, 1974;Bateman, 1975), and in reality it has been solved by chromosomal circularity, terminal protein primers, and telomerases in different extant organisms. Covalently closed hairpin ends can represent another solution to this problem, for example (i) if DNA duplication traverses the hairpin ends and the novel double-stranded sequence joint thus formed is subsequently enzymatically resolved into hairpins that are identical to the parental hairpins or (ii) if nicking, fill-in terminal extension synthesis from the thus generated 3Ј end and rearrangement can form an inward oriented replication fork-like structure (Baroudy et al, 1982;Du and Traktman, 1996;Traktman, 1996) or a primed template for rolling hairpin replication (Cotmore and Tattersall, 1996). Of course, other strategies, such as chromosome circularization before replication followed by linearization of the circular products or even non-semiconservative replication, are also theoretically possible for the Borrelia linear replicons.…”

Cloning the vaccinia virus genome as a bacterial artificial chromosome in Escherichia coli and recovery of infectious virus in mammalian cells

“…The construction of baculovirus and herpesvirus BACs was relatively straightforward: plasmid sequences were inserted by recombination into the circular mature or replicating viral genomes and the latter were propagated in E. coli. Poxvirus genomes, however, are composed of linear double-stranded DNA molecules with covalently closed hairpin ends (19) that are resolved from transient head-to-head or tail-to-tail concatemers during replication (20)(21)(22). Therefore, the method used for cloning baculovirus and herpesvirus genomes seemed inapplicable.…”

Expression of Cloned Vaccinia Virus DNA Sequences Introduced into Animal Cells

“…These unique properties of vaccinia virus suggest that the regulatory sequences of the viral genome might have evolved in a different way to those of the host cell. Indeed, several regions of the vaccinia genome have been sequenced (Venkatesan et al, 1981Baroudy et al, 1982;Pickup et al, 1983), one of which contains the viral thymidine kinase (tk) gene Hruby et al, 1983), and it was found that the consensus sequences normally found at the 5' and 3' end regions of prokaryotic and eukaryotic genes are not present in vaccinia virus DNA. We have previously shown that whole vaccinia virus DNA can be introduced, stably maintained and its presence be associated with some of the changes in the biochemical properties of the transformed cells (Petlicer & Esteban, 1982).…”