Taken together, these results confirm that hyperproliferation is sufficient to induce activation of ATR/Chk1 in purified CD19+ B-cells This, in turn, may indicate that B-cells counteract their vulnerable phase of primary EBV infection mirrored by hyperproliferation by activating the ATR/Chk1-related pathway. The gene discussed is CHEK1; the disease is Epstein-Barr virus infection.