Two defective DNAs of human polyomavirus JC adapted to growth in human embryonic kidney cells.

Human polyomavirus JC (JCV) adapted to growth in human embryonic kidney (HEK) cells contains two or more species of shorter-length viral DNA even after two cycles of plaque purification in HEK cells. We have molecularly cloned JCV DNA from one plaque isolate and determined the physical map of its DNA. Using gel electrophoresis and electron microscopy, we found that the cloned DNA consisted of two classes of JCV DNA. One class of DNA had a deletion of 30% (between 0.7 and 1.0 map units from the EcoRI site) and an insertion of 1% at the same site in the late region. The other had a deletion of 35% (0.18 to 0.53 map units) and an insertion of 12% at the same site in the early region of the JCV genome. Both DNAs had added sequences near the origin of DNA replication. From their structure, the two DNAs appear to complement each other. These results indicate that the HEK-adapted JCV may be replicating by complementation between two defective mutants.