Construction of rat cell lines that contain potential morphologically transforming regions of the herpes simplex...

Hybrid recombinant plasmids were constructed; they were composed of the herpes simplex virus type 2 (HSV2) thymidine kinase (tk) gene and DNA sequences of HSV2 that have been reported to induce morphological and/or oncogenic transformation of rodent cells in culture. Several plasmids were made in two versions, with or without the simian virus 40 enhancer sequences. These plasmids were employed to transfect contact-inhibited Rat-2 tk- cells. It was demonstrated that cell lines with stably integrated, morphologically transforming regions (MTRs) of HSV2 could be isolated at a low frequency. In addition, many cell lines were isolated that had lost the MTR moiety of the transforming plasmids. None of the isolated tk-positive cell lines exhibited significantly altered growth properties when compared to control cell lines. Transient expression of transfecting enhancer plasmids was detectable 40 h posttransfection, but no transformed cell lines were obtained from these experiments. This conflicted with some versions of the 'hit-and-run' hypothesis for HSV-mediated cell transformation.