Phosphorylation of Cdc25A at Ser-123 in response to DNA damage PathwayStep4462 PathwayStep4468 p53-Independent DNA Damage Response In response to DNA damage due to exposure to ultraviolet light or to ionizing radiation, Cdc25A is phosphorylated by Chk1 or Chk2. The phosphorylation of Cdc25A at ser-123, in response to DNA damage from ionizing radiation is a signal for ubiquitination and subsequent degradation of Cdc25A. The destruction of Cdc25A prevents the normal G1/S transition. Cdc25A is required for the activation of the Cyclin E:Cdk2 complexes via dephosphorylation.<p>Chk1 is activated in response to DNA damage due to uv light. However, the phosphorylation occurs at a different site. Pubmed11298456 Reactome Database ID Release 4369610 Reactome, http://www.reactome.org ReactomeREACT_2160 Ubiquitin Mediated Degradation of Phosphorylated Cdc25A