Similarly, in other non-cancer cells RPE-1 (human epithelial cells immortalized with hTERT) and TIG-3 (a normal diploid fibroblast cell line), depletion of CK1γ1 significantly reduced Chk1 activation (by 90% for both), whereas that of Cdc7 reduced it by 60% in both cells (Figure 5—figure supplement 4, lanes 6 and 7), supporting our conclusion that CK1γ1 plays a major role in checkpoint activation in non-cancer cells. This evidence concerns the gene CHEK1 and cancer.