Downstream targets of ATR include the checkpoint kinase 1 (CHK1), which is structurally distinct from CHK2 but has overlapping roles in cell cycle regulation and apoptosis, the Breast Cancer 2 (BRCA2) tumor suppressor, promoting RAD51 catalytic activity and recruitment to DSB sites during, H.R.; and FANCD2, the central executor protein in the repair of DNA cross-links by the Fanconi Anemia (FA) pathway [42]. This evidence concerns the gene CHEK1 and Fanconi anemia.