ATR and Epstein-Barr virus infection: Given that EBV infection of peripheral blood B-cells in vitro was reported to activate ATM and Chk2 but the activation of ATR and Chk1 was not referred to [11], we interrogated whether activation of the ATR/Chk1 dependent pathway is dependent or independent of the infected B-cell origin, i.e., tonsil versus peripheral blood.