The Epstein-Barr virus lytic program is controlled by the co-operative functions of two transactivators

Abstract

The propagation of herpesviruses has long been viewed as a temporally regulated sequential process that results from the consecutive expression of speci®c viral transactivators. As a key step in this process, lytic viral DNA replication is considered as a checkpoint that controls the expression of the late structural viral genes. In a novel genetic approach, we show that both hypotheses do not hold true for the Epstein±Barr virus (EBV). The study of viral mutants of EBV in which the early genes BZLF1 and BRLF1 are deleted allowed a precise assignment of the function of these proteins. Both transactivators were absolutely essential for viral DNA replication. Both BZLF1 and BRLF1 were required for full expression of the EBV proteins expressed during the lytic program, although the respective in¯uence of these molecules on the expression of various viral target genes varied greatly. In replication-defective viral mutants, neither early gene expression nor DNA replication was a prerequisite for late gene expression. This work shows that BRLF1 and BZLF1 harbor distinct but complementary functions that in¯uence all stages of viral production.

The BRRF1 Early Gene of Epstein-Barr Virus Encodes a Transcription Factor That Enhances Induction of Lytic Infection by BRLF1

“…293 cells infected with the R-KO virus (293 R-KO), Z-KO virus (293 Z-KO), and wild-type virus (293 WT) have been described previously (11,14). In the R-KO virus, nucleotides 103,638 to 105,083 (B95.8 coordinates [accession no.…”

“…Stimuli that induce a lytic infection initially activate the transcription of both IE genes (57), and the expression of either IE protein in latently infected cells is sufficient to induce the lytic form of EBV infection (7,8,45,58,64,68). Each IE protein activates the promoter of the other IE gene, and together the two IE proteins then activate the viral early genes and lytic viral replication (2,14).…”

“…The ability of each IE protein to activate transcription of the other IE gene is essential for the disruption of viral latency by either protein (2,14,46,68). Z transactivates the R promoter (Rp) by directly binding to Rp (2,54).…”

HLA-restricted presentation of WT1 tumor antigen in B-lymphoblastoid cell lines established using a maxi-EBV system

“…The advantage of maxi-EBV system is its simplicity; once HEK293 cells harboring maxi-EBVs are established, maxi-EBVs are stably maintained in the cells and can repeatedly produce viruses. A maxi-EBV lacking viral transactivator BZLF1, a critical switch gene for progeny virus production, was previously reported, 33 and similar modification is expected to solve the safety issue of our maxi-EBV system in the future.…”

Epstein-Barr virus interactions with the Bcl-2 protein family and apoptosis in human tumor cells

“…In some microenvironments, EBNA1 is thought to suppress cell death (Kennedy et al, 2003). BARF1 and BZLF1, encoding viral transcription factors, switch the infection from latent to lytic phase (Feederle et al, 2000;Sinclair, 2003). EBV-expressed microRNAs (miRNAs) play a crucial role in development, the cell cycle, and immunity and contribute to cancerassociated pathology (Lee and Dutta, 2009;Forte and Luftig, 2011).…”