Regulation of Autophagic Activation by Rta of Epstein-Barr Virus via the Extracellular Signal-Regulated Kinase Pathway

Autophagy is an intracellular degradation pathway that provides a host defense mechanism against intracellular pathogens. However, many viruses exploit this mechanism to promote their replication. This study shows that lytic induction of Epstein-Barr virus (EBV) increases the membrane-bound form of LC3 (LC3-II) and LC3-containing punctate structures in EBV-positive cells. Transfecting 293T cells with a plasmid that expresses Rta also induces autophagy, revealing that Rta is responsible for autophagic activation. The activation involves Atg5, a key component of autophagy, but not the mTOR pathway. The expression of Rta also activates the transcription of the genes that participate in the formation of autophagosomes, including LC3A, LC3B, and ATG9B genes, as well as those that are involved in the regulation of autophagy, including the genes TNF, IRGM, and TRAIL. Additionally, treatment with U0126 inhibits the Rta-induced autophagy and the expression of autophagy genes, indicating that the autophagic activation is caused by the activation of extracellular signal-regulated kinase (ERK) signaling by Rta. Finally, the inhibition of autophagic activity by an autophagy inhibitor, 3-methyladenine, or Atg5 small interfering RNA, reduces the expression of EBV lytic proteins and the production of viral particles, revealing that autophagy is critical to EBV lytic progression. This investigation reveals how an EBV-encoded transcription factor promotes autophagy to affect viral lytic development. IMPORTANCE Autophagy is a cellular process that degrades and recycles nutrients under stress conditions to promote cell survival. Although autophagy commonly serves as a defense mechanism against viral infection, many viruses exploit this mechanism to promote their replication. This study finds that a transcription factor that is encoded by Epstein-Barr virus (EBV), Rta, activates autophagy, and the inhibition of autophagy reduces the ability of the virus to express viral lytic proteins and to generate progeny. Unlike other virus-encoded proteins that modulate autophagy by interacting with proteins that are involved in the autophagic pathway, Rta activates the transcription of the autophagy-related genes via the ERK pathway. The results of this study reveal how the virus manipulates autophagy to promote its lytic development.