| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1987: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1986: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
It has been well established that the proliferation of mammalian cells is regulated by transition of cells between resting state (Go phase) and growing state (growing cycle). We have isolated a temperature-sensitive mutant clone, tsJT60, from a Fischer rat cell line. tsJT60 satisfies the following criteria of Go mutant, i.e. it grows normally at both permissive (34゜C) and nonpermissive temperature (40゜C) in an exponential growth phase, but when stimulated by serum to leave Go phase it enters at the permissive temperature but not at the nonpermissive temperature.
Although tsJT60 cells do not enter S phase from Go phase following stimulation with serum at 40゜C, the sequential expression of growth-regulated genes such as c-fos, c-myc, KC, JE, p_<53>, and ornithine decarboxylase occurs at 34゜C as well as at 40゜C. Expression of histone gene is blocked at 40゜C in consistent with the block of entry into S phase. Thus, the signal of growth induction can reach nuclear genome even at 40゜C.
Although tsJT60 cells do not enter S phase from Go phase at 40゜C following growth stimulation with either serum or epidermal growth factor (EGF), they do so following stimulation with both serum and EGF. Insulin and transferrin have similar, though very weak, effect as EGF. Sequential treatment of cells with serum and EGF has no stimulatory effect, and simultaneous presence of both factors is required for cells to progress toward S phase at 40゜C.
tsJT60 cells become highly lethal at 40゜C following transformation with adenovirus 5 E1B deletion mutant.These transformed tsJT60 clones are hopefully to be used for cloning of mutated gene of tsJT60.
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