Identification of unintegrated forms of Kirsten murine sarcoma viral DNA and restriction endonuclease cleavage map of linear DNA

We detected unintegrated linear 7.0-kilobase pair DNA and covalently closed circular DNA species in NIH3T3 cells recently infected with Kirsten murine sarcoma virus. Using the linear DNA, we constructed a restriction endonuclease cleavage map and compared it with the map of Harvey murine sarcoma virus. The restriction endonuclease maps of two segments, one 1.2 kilobase pairs (SmaI site) to 3.7 kilobase pairs (HindIII site) from the right end (corresponding to the viral 3' side) and the other 0.5 kilobase pair (SmaI and KpnI sites) to 0.9 kilobase pair (KpnI site) from the left end, were identical in the two virus types.