Cell cycle analysis of Epstein-Barr virus-infected cells following treatment with lytic cycle-inducing agents

While Epstein-Barr virus (EBV) latency-associated gene expression is associ ated with cell cycle progression, the relationship between the EBV lytic pr ogram and the cell cycle is less clear. Using four different EBV lytic indu ction systems, we address the relationship between lytic cycle activation a nd the cell cycle. In three of these systems, G(0) or G(1) cell growth arre st signaling is observed prior to detection of the EBV immediate-early gene product Zta, In tetradecanoyl phorbol acetate-treated P3HR1 cultures and i n 5-iodo-2'-deoxyuridine-treated NPC-KT cultures, cell cycle analysis of Zt a-expressing cell populations showed a significant G(1) bias during the ear ly stages of lytic cycle progression. In contrast, treatment of the cell li ne Akata with anti-immunoglobulin (Ig) results in rapid induction of immedi ate-early gene expression, and accordingly, activation of the immediate-ear ly gene product Zta precedes significant anti-Ig-induced cell cycle effects . Nevertheless, cell cycle analysis of the Zta-expressing population follow ing anti-Ig treatment shows a bias for cells in G(1), indicating that anti- Ig-mediated induction of Zta occurs more efficiently in cells traversing: G (1), Last, although 5-azacy-tidine treatment of Rael cells results in a G(1 ) arrest in the total cell population which precedes the induction of Zta, cell cycle analysis of the Zta-expressing population shows a significant bi as for cells with an apparent G(2)/M DNA content, This bias may result, in part, from activation of Zta expression following demethylation of the Zta promoter during S-phase, Together, these studies indicate that induction of Zta occurs through several distinct mechanisms, some of which may involve checkpoint signaling.