title: Herpes simplex virus thymidine kinase gene is stably maintained and expressed in cells transformed by protoplast fusion.
abstract: We examined a series of transformed cell lines resulting from transfer of the herpes simplex virus type 1 thymidine kinase gene to Ltk- cells by protoplast fusion gene transfer. We show that multiple copies of the transforming plasmid DNA, ranging from a minimum of two to greater than 20, were present in one or at most a few integration sites in each cell line. The TK+ phenotype was stable in five independent transformed cell lines after growth in nonselective medium for over a year. Transforming plasmid DNA was stable in one cell line containing from two to five copies after a year of growth in nonselective medium. In another cell line initially containing about 20 copies, the transforming DNA became rearranged soon after growth to mass culture, resulting in a decrease to two to five copies which then remained stably maintained. This suggests that TK+ transformants resulting from protoplast fusion are stable when the input DNA has integrated in a relatively low copy number.
mesh_terms: D000818:Animals; D002460:Cell Line; D002472:Cell Transformation, Viral; D004262:DNA Restriction Enzymes; D004926:Escherichia coli / Q000235:genetics; D005796:Genes; D005814:Genes, Viral; D009693:Nucleic Acid Hybridization; D010957:Plasmids; D011523:Protoplasts / Q000502:physiology; D018139:Simplexvirus / Q000201:enzymology / Q000235:genetics*; D013937:Thymidine Kinase / Q000235:genetics*
chemical_list: D013937:Thymidine Kinase; D004262:DNA Restriction Enzymes