DNA-mediated cotransfer of unlinked mammalian cell markers into mouse L cells.

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Abstract
Purified DNA from 3 different types of mammalian cells was precipitated with calcium phosphate and added to mouse L [neoplastic fibroblast] cells deficient in thymidine kinase (TK). Donor DNA was prepared from 3 cell lines: mouse cells transfected with UV-inactivated herpes simplex virus (HSV) type 1, or a purified fragment of HSV carrying the TK gene; human HeLa [cervical carcinoma] cells; and CHO [Chinese hamster ovary cells]. Several hypoxanthine-aminopterin-thymidine resistant colonies were isolated from each experiment. The origin of the TK that is expressed in these cells was studied by polyacrylamide gel electrophoresis, isoelectric focusing, or heat stability. The TK in all instances was of the donor origin. To determine the extent of gene transfer the CHO and HeLa DNA transfectants were assayed for galactokinase (GALK), a marker closely linked to TK,and 25 other isozymes representing a large number of different chromosomes. No cotransfer of GALK was observed, indicating that the size of the transferred DNA segment is limited. In one instance, esterase-D, an unlinked marker of Chinese hamster origin, was transferred along with TK. Nonselected markers can be transferred by this method, although at a low efficiency.