p53 C-Terminal Phosphorylation by CHK1 and CHK2 Participates in the Regulation of DNA-Damage-induced C-Terminal Acetylation

TLDR

p53 is a tumor suppressor that mediates growth arrest or apoptosis and protects genome integrity, and its activity is regulated by phosphorylation and acetylation in response to DNA damage. This study seeks to characterize the C‑terminal phosphorylation of p53 by the kinases CHK1 and CHK2. The authors employed tryptic phosphopeptide mapping to identify CHK1/CHK2 phosphorylation sites in the final 100 amino acids of p53. They discovered six CHK1/CHK2 sites, demonstrated that DNA damage induces phosphorylation at Ser366, Ser378, and Thr387, and showed that these modifications modulate C‑terminal acetylation and p53‑target promoter activation, indicating an interplay between phosphorylation and acetylation controlled by CHK1/CHK2.

Abstract

The tumor suppressor protein p53 mediates stress-induced growth arrest or apoptosis and plays a major role in safeguarding genome integrity. In response to DNA damage, p53 can be modified at multiple sites by phosphorylation and acetylation. We report on the characterization of p53 C-terminal phosphorylation by CHK1 and CHK2, two serine/threonine (Ser/Thr) protein kinases, previously implicated in the phosphorylation of the p53 N terminus. Using tryptic phosphopeptide mapping, we have identified six additional CHK1 and CHK2 sites residing in the final 100 amino acids of p53. Phosphorylation of at least three of these sites, Ser366, Ser378, and Thr387, was induced by DNA damage, and the induction at Ser366 and Thr387 was abrogated by small interfering RNA targeting chk1 and chk2. Furthermore, mutation of these phosphorylation sites has a different impact on p53 C-terminal acetylation and on the activation of p53-targeted promoters. Our results demonstrate a possible interplay between p53 C-terminal phosphorylation and acetylation, and they provide an additional mechanism for the control of the activity of p53 by CHK1 and CHK2.