FIG. 3.

PCNA mRNA levels in irradiated CREF cells. Total cell RNA was prepared from unirradiated (lane 1) or irradiated (lanes 2 to 5) CREF cells kept in DMEM containing 0.1% FBS at the indicated times postexposure to 12 Gys of IR. Each sample (30 μg) was fractionated in a formaldehyde-agarose gel that was subsequently transferred to a polyvinylidene difluoride membrane. The blot was probed by hybridization to radioactive cDNA probes specific for β-actin and PCNA. The hybridized filter was exposed to X-ray film with an intensifying screen for 48 h.