Phosphorylation and activation of Chk1 by ATM Phosphorylation of Cdc25A at Ser-123 by Chk1 Phosphorylation of Cdc25A at Ser-123 by Chk2 Proteolytic degradation of ubiquitinated-Cdc25A Ubiquitination of phosphorylated Cdc25A PathwayStep4465 PathwayStep4466 PathwayStep4463 PathwayStep4464 PathwayStep4467 Ubiquitin Mediated Degradation of Phosphorylated Cdc25A Pubmed10828887 Reactome Database ID Release 4369601 Reactome, http://www.reactome.org ReactomeREACT_1614 cdc25A protein is degraded by the ubiquitin-proteasome machinery in both terminally differentiating and cycling cells (Bernardi et al. 2000).