p53 Phosphorylation and Association with Murine Double Minute 2, c-Jun NH2-Terminal Kinase, p14ARF, and p300/CBP during the Cell Cycle and after Exposure to Ultraviolet Irradiation

p53 phosphorylation and association with proteins is implicated in its stability and activity. We have compared the association of DNA-bound and overall pools of p53 with murine double minute 2 (Mdm2), c-Jun NH 2 -terminal kinase (JNK), p300/CBP, and p14 ARF during cell cycle progression. Whereas DNA-bound p53 associates with JNK at G 0 -G 1 and with Mdm2 and p300 during S and G 2 -M phases, the general pool of p53 was found in complex with JNK and Mdm2 almost throughout the cell cycle. Phosphorylation of p53 at serines 9, 15, and 20 is at the highest levels at G 1 and at serines 37 and 392 during G 2 -M phase. Whereas a high dose of UV irradiation was required for phosphorylation of serines 15 and 392 between 8 and 24 h after treatment, a low dose caused immediate phosphorylation on serines 9, 20, and 372. These dynamic changes in the phosphorylation of p53 are expected to play a pivotal role in p53 association, stability, and function.