Rta is the principal activator of Epstein-Barr virus epithelial lytic transcription

Abstract

The transition from latent Epstein-Barr virus (EBV) infection to lytic viral replication is mediated by the viral transcription factors Rta and Zta. Although both are required for virion production, dissecting the specific roles played by Rta and Zta is challenging because they induce each other’s expression. To circumvent this, we constructed an EBV mutant deleted for the genes encoding Rta and Zta (BRLF1 and BZLF1, respectively) in the Akata strain BACmid. This mutant, termed EBVΔRZ, was used to infect several epithelial cell lines, including telomerase-immortalized normal oral keratinocytes, a highly physiologic model of EBV epithelial cell infection. Using RNA-seq, we determined the gene expression induced by each viral transactivator. Surprisingly, Zta alone only induced expression of the lytic origin transcripts BHLF1 and LF3. In contrast, Rta activated the majority of EBV early gene transcripts. As expected, Zta and Rta were both required for expression of late gene transcripts. Zta also cooperated with Rta to enhance a subset of early gene transcripts (Rtasynergy transcripts) that Zta was unable to activate when expressed alone. Interestingly, Rta and Zta each cooperatively enhanced the other’s binding to EBV early gene promoters, but this effect was not restricted to promoters where synergy was observed. We demonstrate that Zta did not affect Rtasynergy transcript stability, but increased Rtasynergy gene transcription despite having no effect on their transcription when expressed alone. Our results suggest that, at least in epithelial cells, Rta is the dominant transactivator and that Zta functions primarily to support DNA replication and co-activate a subset of early promoters with Rta. This closely parallels the arrangement in KSHV where ORF50 (Rta homolog) is the principal activator of lytic transcription and K8 (Zta homolog) is required for DNA replication at oriLyt.

Epstein-Barr virus BRRF1 induces butyrophilin 2A1 in nasopharyngeal carcinoma cells via the IL-22/JAK3-STAT3 pathway

“…Indeed, overexpression of the BRRF1 in NPC43 upregulated the expression of JAK3 and RhoB genes while downregulating the IL22RA2 gene (Figure 3A). The other genes showed no statistically significant differences (Figure S2 and diseases and are involved in regulating cancer and homeostasis [26]. Therefore, the mRNA and protein downregulation of IL22RA2 in NPC43 cells (Figure 3A and 3B)…”

Tegument proteins of Epstein-Barr virus: Diverse functions, complex networks, and oncogenesis

“…BRLF1 is one of the two IE genes encoded by EBV implicated in viral reactivation. This transcriptional activator is required for lytic initiation, particularly in differentiated epithelial cells [ 222 ]. BRLF1 protein is incorporated into the tegument [ 19 ] and binds a capsid triplex protein, BORF1, thereby preventing its ubiquitin-dependent degradation in transfected cells [ 19 ].…”

Immunological Aspects of EBV and Oral Mucosa Interactions in Oral Lichen Planus

“…Both Rta and Zta are immediate early transcription factors that activate EBV-lytic gene expression. The products of the early genes are mainly involved in viral DNA replication, while the products of the late genes mainly support the formation of viral particles [103]. The lytic cycle of EBV is triggered when EBV-infected memory B cells differentiate into plasma cells, simultaneously stimulating productive EBV replication by releasing large amounts of EBV fragments that directly infect epithelial cells of the oropharynx.…”