Chk2/hCds1 functions as a DNA damage checkpoint in G₁by stabilizing p53

TLDR

Chk2/hCds1 is a human DNA‑damage checkpoint kinase homologous to yeast RAD53/SPK1 and cds1 that is post‑translationally modified after damage and phosphorylates Cdc25C, suggesting a role in G2 arrest. The authors expressed Chk2/hCds1 in human cells and examined the resulting cell‑cycle profiles. Wild‑type Chk2/hCds1, but not a catalytically inactive mutant, triggers DNA‑damage–induced G1 arrest by phosphorylating p53 on Ser‑20, disrupting its Mdm2 complex, stabilizing p53, and acting upstream of p53, whereas dominant‑negative mutants abolish these effects.

Abstract

Chk2/hcds1, the human homolog of the Saccharomyces cerevisiae RAD53/SPK1 and Schizosaccharomyces pombe cds1 DNA damage checkpoint genes, encodes a protein kinase that is post-translationally modified after DNA damage. Like its yeast homologs, the Chk2/hCds1 protein phosphorylates Cdc25C in vitro, suggesting that it arrests cells in G(2) in response to DNA damage. We expressed Chk2/hCds1 in human cells and analyzed their cell cycle profile. Wild-type, but not catalytically inactive, Chk2/hCds1 led to G(1) arrest after DNA damage. The arrest was inhibited by cotransfection of a dominant-negative p53 mutant, indicating that Chk2/hCds1 acted upstream of p53. In vitro, Chk2/hCds1 phosphorylated p53 on Ser-20 and dissociated preformed complexes of p53 with Mdm2, a protein that targets p53 for degradation. In vivo, ectopic expression of wild-type Chk2/hCds1 led to increased p53 stabilization after DNA damage, whereas expression of a dominant-negative Chk2/hCds1 mutant abrogated both phosphorylation of p53 on Ser-20 and p53 stabilization. Thus, in response to DNA damage, Chk2/hCds1 stabilizes the p53 tumor suppressor protein leading to cell cycle arrest in G(1).