The interaction of a topoisomerase-like enzyme from herpes simplex virus type 1-infected cells with non-viral circular DNA.

An enzyme activity from herpes simplex virus type 1 (HSV-1)-infected baby hamster kidney cells has been identified which generates large networks of pBR322 DNA from a monomeric DNA substrate. Extracts derived from cells infected at the non-permissive temperature, with the early regulatory mutants of HSV-1, tsK and tsB2, did not contain activity, suggesting that the enzyme is virus-induced and may be virus-specific. The enzyme is similar to the DNA topoisomerases in that network formation was dependent upon the presence of Mg2+ and a DNA condensing agent, and ATP was not required. Following digestion with EcoRI, the networks could be resolved to a single, linear, monomeric species of pBR322 DNA.