Isolation of polyoma viruses lacking endonuclease hindlll sites

Abstract

Spontaneous mutants of polyoma virus have been isolated which lack either one or both of the two endo HindIII cleavage sites present in polyoma DNA. Some of the mutants contain single base changes or small deletions at the HindIII site in the early region of the polyoma genome. Most of these mutants have a normal phenotype; however, one member of this group grows poorly in comparison with wild-type virus. Other mutants contain large deletions, have lost either of the HindIII sites, and appear to require complementation by helper viruses in order to complete their growth cycle.