title: Prolongation of duration of G2 arrest delays and finally blocks entry into M phase in contrast to stable and reversible G1 arrest: study of a G1/G2 temperature-sensitive mutant of rat 3Y1 fibroblasts.
abstract: Proliferation of 3Y1tsF121 cells was arrested in G1 and G2 phases after a shift up to 39.8 degrees C (restrictive temperature). Both arrests were reversible: after a shift down to 33.8 degrees C (permissive temperature), these cells effectively entered the next phases. However, the entry into M phase of the G2-arrested cells was delayed depending on the time in arrest. The G2-arrested cells finally became incapable of entering M phase with a prolonged incubation at 39.8 degrees C. Under the same condition, G1-arrested cells did not lose their ability to proliferate, and their delay of entry into S phase was slight. Therefore, cells in G2 phase are, in a sense, more unstable than the cells in G1 phase. These results also suggest that the time required for entry into M phase may depend on the preparedness for the initiation of M phase and, that it may be prolonged under the condition where the preparedness for entry into M phase is diminished.
mesh_terms: D000818:Animals; D016590:Aphidicolin; D002453:Cell Cycle; D002455:Cell Division; D002460:Cell Line; D004247:DNA / Q000032:analysis; D004224:Diterpenes / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology*; D007399:Interphase; D009154:Mutation; D051381:Rats; D013696:Temperature
chemical_list: D004224:Diterpenes; D016590:Aphidicolin; D004247:DNA