CHEK1 and Fanconi anemia: Upon activation of the repair mechanism, ATR phosphorylates checkpoint kinase 1 (CHK1), halting the cell cycle, initiating the non-homologous end joining (NHEJ) repair process via phosphorylation of MRE11, and activating the Fanconi anaemia (FA) pathway, thereby promoting homologous recombination (HR) repair of DNA damage (Figure 3(b)).126–128