Stimulation of DNA Synthesis and Enhancement of Murine Sarcoma Virus Replication in Mouse Embryo Cells by SV 40

Mouse embryo cells maintained on a rigid subculture regime undergo a rapid decline in growth rate leading to a period of negligible growth. Eventually the cells recommence growth and become established in vitro (Todaro & Green, 1963; Aaronson & Todaro, 1968; Baker & Simons, 1971). A very small percentage of cells in the non-dividing phase incorporate [3H]-thymidine and cells in this phase are not transformed by murine sarcoma virus (Baker & Simons, 1971). Treatment with colchicine does not result in the detection of metaphases and cells in this phase have been termed ‘amitotic’ (Baker & Simons, 1971).

Cellular DNA synthesis has been shown to be induced in resting cells by SV 40 (Girardi, Jensen & Koprowski, 1965; Coggin, 1969). Consequently it was possible that SV 40 would be able to induce DNA synthesis in the amitotic mouse cells rendering them susceptible to MSV.

The standard method of cultivating the cells has been described in detail previously (Baker & Simons, 1971).