EpsteinBarr virus (EBV) Rta-mediated cell cycle arrest enables permissive replication of EBV and Kaposis sarcoma-associated herpesvirus in 293 cells

Epstein-Barr virus (EBV) Rta is a latent-lytic molecular switch evolutionarily conserved in all gamma-herpesviruses. In previous studies, doxycycline-inducible Rta was shown to potently produce an irreversible G1 arrest followed by cellular senescence in 293 cells. Here, we demonstrate that in this system the inducible Rta not only reactivates resident genome of EBV but also that of Kaposis sarcoma-associated herpesvirus (KSHV), to similar efficiency. However, Rta-induced senescence program was terminated by the robust viral lytic cycle replication that eventually caused cell death. Furthermore, prior to the abrupt expression of immediate-early protein (EBV BZLF1 or KSHV RTA), Rta simultaneously down-regulates cell cycle activators (c-Myc, CDK6, CCND2) and up-regulates senescence-related genes (p21, 14-3-3s). Since Rta is a viral immediate-early transcriptional activator, it is envisioned that during the initial stage of viral reactivation, Rta may engage to modulate the host transcriptome, to halt cell cycle progression, and to maintain an ideal environment for manufacturing infectious virions.

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Chen YJ, Tsai WH, Chen YL, Ko YC, Chou SP, Chen JY, Lin SF