Characterization of ts13 cells a temperature-sensitive mutant of the G1 phase of the cell cycle |
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Authors: | J Floros T Ashihara R Baserga |
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Institution: | 1. Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA;1. Program for Nurturing Global Leaders in Tropical and Emerging Communicable Diseases, Graduate School of Biomedical Sciences, Nagasaki University, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan;2. Department of Protozoology, Institute of Tropical Medicine (NEKKEN), Nagasaki University, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan;1. Department of Biochemistry, University of Calcutta, 35, Ballygunge Circular Road, Kolkata 700 019, West Bengal, India;2. Mitra Tower, Lake Town, Block-A, Kolkata 700 089, India;3. Department of Pediatric Medicine, Institute of Post Graduate Medical Education & Research, Kolkata, West Bengal, India |
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Abstract: | ts 13 cells are a temperature-sensitive (ts) mutant of BHK cells that are known to arrest in G1 when shifted to the nonpermissive temperature. We have determined the entry into S of ts13 cells in five different growth conditions, namely: 1) quiescent, sparse cultures stimulated to proliferate by serum. 2) Quiescent, dense cultures stimulated by serum. 3) Quiescent, sparse cultures stimulated by trypsinization and replating. 4) Quiescent, dense cultures stimulated by trypsinization and replating. 5) Mitotic cells collected by mitotic detachment. For each different growth condition we have also determined the execution point of the mutant function, i.e. the time at which a shift-up to the nonpermissive temperature no longer prevents the entry of cells into S. The median time of entry into S and the execution point varied in different growth conditions, but the distance between the median execution point and the median time of entry into S was remarkably constant, i.e. 3.2 hr. In addition we have fused ts 13 cells cells with chick erythrocytes and studied the ability of ts13 cells in heterokaryon formation to induce DNA synthesis in chick nuclei. Although ts13 cells can induce DNA synthesis in chick nuclei at the permissive temperature, they fail to do so when fused and stimulated at the nonpermissive temperature of 39.5 degrees C. |
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