DNA sequences required for the initiation of adenovirus type 4 DNA replication in vitro.
In-vivo studies have demonstrated that adenovirus type 2 and adenovirus type 4 have different DNA sequence requirements for the initiation of DNA replication. To investigate the basis of these differences an in-vitro system has been developed which will faithfully initiate adenovirus type 4 DNA replication. A plasmid containing 140 base-pairs of the right terminus of adenovirus type 4 supported initiation of DNA replication in vitro, provided that the plasmid was linearized in such a way as to locate the viral terminal sequences at the molecular ends of the DNA. Initiation by adenovirus type 4-infected cell extracts was also supported by a plasmid containing the complete adenovirus type 2 inverted terminal repeat (ITR). Deletion analysis of both adenovirus types 2 and 4 ITRs revealed that only the terminal 18 base-pairs of the genomes (perfectly conserved between the 2 viruses) were required for initiation in vitro. Thus, initiation was not enhanced by the presence of either the NFI site, the NFIII site or both sites together. Fractionation of a HeLa cell nuclear extract, by ion-exchange chromatography, identified a nuclear factor that stimulated the initiation reaction four- to fivefold. The stimulatory factor did not correspond to either of the cellular proteins NFI or NFIII which stimulate adenovirus type 2 DNA replication in vitro. Initiation in vitro was also supported by single-stranded DNA templates, albeit at a lower efficiency. Studies with synthetic oligonucleotides indicated a surprising specificity for initiation: whereas the strand used as template during initiation in vivo was active as a template for initiation in vitro, the complementary strand was inactive.
MRC Virology Unit, Glasgow, Scotland.
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Harris
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Hay
D000256:Adenoviridae / Q000502:physiology*; D001483:Base Sequence; D004261:DNA Replication; D004279:DNA, Viral; D006367:HeLa Cells; D006801:Humans; D009154:Mutation; D009838:Oligodeoxyribonucleotides; D010957:Plasmids; D013698:Templates, Genetic; D014779:Virus Replication
D004279:DNA, Viral; D009838:Oligodeoxyribonucleotides