p53 is not required for regulation of apoptosis or radioprotection by interleukin-3.

Primary interleukin-3 (IL-3)-dependent mast cell cultures from bone marrow of p53-null mice and littermate controls were established. Both p53-null and wild-type cells entered apoptosis on IL-3 removal, showing that p53 is not required for entry into apoptosis after factor deprivation. After X-irradiation, a lower proportion of the p53-null than wild-type cells underwent G2 arrest, but their radiosensitivity was similar. An IL-3-dependent cell line expressing wild-type p53 was used to show that cells die at a fixed time after X-irradiation rather than from a specific cell cycle point.