Evidence that Replication Initiates at only Some of the Potential Origins in Each Oligomeric Form of Bovine Papillomavirus Type 1 DNA

J. B. Schvartzman, S. Adolph, L. Martin-Parras, C. L. Schildkraut

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Abstract

In a subclone of ID13 mouse fibroblasts latently infected with bovine papillomavirus type 1 (BPV-1) DNA, the viral genome occurred as a mixture of extrachromosomal circular monomers and oligomers. Multiple copies were also associated with the host cell genome, predominantly at a single site in a head-to-tail tandem array. We examined the replicative intermediates of extrachromosomal forms of BPV-1 DNA by using two-dimensional gel electrophoresis. The results obtained indicate that initiation of DNA replication occurred near the center of the EcoRI-BamHI 5.6-kilobase fragment. In some molecules, however, this fragment was replicated from one end to the other by means of a single fork initiated elsewhere. Termination also occurred within this fragment. The EcoRI-BamHI 2.3-kilobase fragment replicated as a DNA molecule containing a termination site for DNA replication and also by means of a single fork traversing the fragment from one end to the other. Thus, replication forks proceeded through these fragments in different manners, apparently depending on whether they were part of a monomer, a dimer, a trimer, or higher oligomers. These observations lead to the conclusion that initiation of DNA replication in BPV-1 DNA takes place at or close to plasmid maintenance sequence 1. From this point, replication proceeds bidirectionally and termination occurs approximately 180° opposite the origin. The results obtained are consistent with one or more replication origins being quiescent in BPV-1 DNA oligomers.

Original languageEnglish (US)
Pages (from-to)3078-3086
Number of pages9
JournalMolecular and cellular biology
Volume10
Issue number6
DOIs
StatePublished - Jun 1990

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ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology

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