Characterization of the replicative structures of the DNA of a herpesvirus (pseudorabies).

The replication of PRV DNA occurs in two phases, early and late. During the early stages of infection newly synthesized DNA is associated with molecules sedimenting with an S-value up to two-fold greater than that of mature viral DNA. These molecules represent unit-size linear or circular molecules, as well as small concatemers in the process of replication. Initiation of replication occurs at a site situated 20 micron from one of the ends as well as at or near the end of the molecules. At later times, newly synthesized DNA is associated with large, "tangled" concatemers containing single-stranded segments of DNA. Our results indicate that at least some of the single-stranded DNA may be produced during the extraction procedure. Analysis of the large, "tangled" concatemers with restriction enzymes shows that they consist of linear arrays of viral DNA molecules.