Further Description of a Temperature-Sensitive Mammalian Cell Mutant Exhibiting Micronucleation

Abstract

The temperature-sensitive mutant, ts 39, has been shown to undergo micronucleation upon exposure to a non-permissive temperature (39°C), a phenomenon which resembles micronucleation induced by colchicine. Ts 39 cells, however, have the same sensitivity to colchicine as their parent cells. The amount of colchicine-binding activity of intracellular materials in ts 39 cells cultured at a permissive temperature (33.5°C) was essentially equal to that for parent cells, and the amount after exposure to 39°C (0-3 days) was directly proportional to the number of viable cells. These results suggest that both the nature and amounts of tubulin in ts 39 cells do not differ from those in the parent cells.The morphological alteration of ts 39 cells preceding micronucleation was studied using adhering cells derived from ts 39. The nuclei of almost all cells were deformed and lobulated, and some of them appeared to segment into multimicronuclei. Mutant cells in suspension showed similar morphological changes. Cell cycle and cytofluorometric studies were performed and the results suggest that multimicronucleation starts during the period of mitotic and G1-phase after exposure to non-permissive temperatures.