“…Consistent with previous reports (Agrawal et al, 1996), p27 Kip1 was expressed at high levels in quiescent 3T3 cells but gradually declined to very low levels by 12 ± 15 h after serum stimulation, the time at which the cells are entering into S phase (Ouyang et al, 1993). Surprisingly, however, no p27 Kip1 was detected in the nuclear fraction at any time point.…”