Insertion of a New Gene of Viral Origin into Bone Marrow Cells of Mice

DNA containing the herpes simplex virus thymidine kinase (HSVtk) gene was used to transform wild-type tk$^{+}$ mouse L cells to a tk$^{++}$ status in vitro using methotrexate as a selective agent. HSVtk DNA was also used to transform mouse bone marrow cells in vitro. Transformed marrow cells injected into irradiated and methotrexate-treated recipient mice gave rise to proliferating cells which in some cases dominated the marrow population and which contained HSVtk gene sequences.