Isolation of ts mutant cells which arrest in G1/G0 phase at the non-permissive temperature in the presence of appropriate growth factors from a Fischer rat cell line, 3Y1.

Two types of cell-cycle-ts mutants were isolated from Fischer rat cell line, 3Y1, and characterized. Clones in one complementation group, tsJT51 and tsJT341, grew at 34 degrees C in the presence of 10% fetal bovine serum (FBS). When the cells growing at 34 degrees C were transferred to 39.5 degrees C, they were arrested alive in G1/G0 phase in the presence of both FBS and epidermal growth factor (EGF), but died in the presence of one of these growth factors. The cells in the other complementation group, tsJT59, tsJT308, tsJT314 and tsJT349, grew at 34 degrees C in the presence of 10% FBS. When the cells growing at 34 degrees C were transferred to 39.5 degrees C, they were arrested alive in G1/G0 phase in the simultaneous presence of FBS, EGF and insulin, but died quickly if one of these growth factors was lacking. Growth-arrested cells at 39.5 degrees C were viable at least one or two weeks and had a potency to resume growth following the shift-down of temperature. Those are assumed to be ts mutant cells which enter and stay in G1/G0 phase from the cell cycle at the non-permissive temperature only in the presence of appropriate growth factors.