Cell cycle structure and apoptosis of E1Aad5-immortalized rat cells upon exposure to DNA-damaging agents

Normal rat embryo fibroblasts and immortalized cell lines derived therefrom using oncogene E1Aad5 were assessed for their ability to stop in the G1 and G2 phases upon exposure to gamma-irradiation, far UV, and serum-depleted medium. Normal fibroblasts and EIA 12S-immortalized cells containing wild-type p53 were capable of such cell cycle arrest, while EIA(12S+13S)-immortalized variants having both wild-type and mutant p53 could not stop at G1. A distinguishing feature of the EIA-expressing lines was their high sensitivity to the specified damaging agents, which caused apoptosis as revealed morphologically and electrophoretically (nucleosome fragmentation). The most sensitive were the E1A(12S+13S) cells, which also died under standard cultivation conditions. The possible mechanisms of cell cycle arrest and apoptosis of the immortalized lines are discussed.