Characterization of a metastable, partially replicated dimeric intermediate of minute virus of mice

Intracellular, replicative-form DNA of minute virus of mice was characterized by agarose gel electrophoresis, velocity sedimentation, electron microscopy, restriction endonuclease digestion, and sensitivity to the single-stranded nuclease S1. This analysis demonstrated the presence in murine cells infected with minute virus of mice of a 10.0-kilobase pair dimer replicative form, a 5-kilobase pair monomer replicative form, as well as a 5-kilobase viral single-stranded DNA species. Two additional viral DNA species that migrated in 0.5% agarose gels with apparent sizes of 8.0 and 5.5 kilobase pairs were also observed. Further investigation indicated that the 8.0-kilobase pair DNA represents a novel class of metastable, partially replicated, dimeric intermediates. This finding has important implications for the mechanism of parvovirus DNA replication.