Presence of a herpes simplex virus type 1 genome fragment in HSV-transformed cells

LTK-cells infected with UV-irradiated HSV produce transformants that contain a thymidine kinase (TK) activity not found in the parental LTK-line (Munyon et al., 1971). One of these (TK+) transformants (clone 139) has been analysed for the presence of the HSV genome. Reassociation kinetics studies with iodinated HSV DNA of specific activity of about 9 x 107 cpm/mug have established that there are approximately six copies of a fragment comprising about 15% of the HSV genome in HSV-transformed clone 139. Neither the parental LTK-nor a "revertant" cell line (clone 139 BUDR) obtained from clone 139 showed any detectable HSV-specific sequences. Analysis of data on RNA-125I-HSV DNA reassociation kinetics indicates that perhaps 5% of the HSV genome is transcribed in HSV-transformed clone 139. These results indicate that transformation is probably maintained by the presence of only a fraction of the HSV genome in the TK+ clones.