Latency of Epstein-Barr virus is stabilized by antisense-mediated control of the viral immediate-early gene BZLF-1

Abstract

The ability of the Epstein-Barr virus (EBV) to avoid lytic replication and to establish a latent infection in B-lymphocytes is fundamental for its lifelong persistence and the pathogenesis of various EBV-associated diseases. The viral immediate-early gene BZLF-1 plays a key role for the induction of lytic replication and its activity is strictly regulated on different levels of gene expression. Recently, it was demonstrated that BZLF-1 is also controlled by a posttranscriptional mechanism. Transient synthesis of a mutated competitor RNA saturated this mechanism and caused both expression of the BZLF-1 protein and the induction of lytic viral replication. Using short overlapping fragments of the competitor, it is shown that this control acts on the unspliced primary transcript. RT-PCR demonstrated unspliced BZLF-1 RNA in latently infected B-lymphocytes in the absence of BZLF-1 protein. Due to the complementarity of the gene BZLF-1 and the latency-associated gene EBNA-1 on the opposite strand of the genome, we propose an antisense-mediated mechanism. RNase protection assays demonstrated transcripts in antisense orientation to the BZLF-1 transcript during latency, which comprise a comparable constellation to other herpesviruses. A combined RNAse protection/RT-PCR assay detected the double-stranded hybrid RNA, consisting of the unspliced BZLF-1 transcript and a noncoding intron of the EBNA-1 gene. Binding of BZLF-1 transcripts is suggested to be an important backup control mechanism in addition to transcriptional regulation, stabilizing latency and preventing inappropriate lytic viral replication in vivo.

The DNA virus Invertebrate iridescent virus 6 is a target of the Drosophila RNAi machinery

“…Antisense transcription is prevalent among different families of DNA viruses, and it has been suggested to affect viral gene expression (48)(49)(50)(51)(52). Antisense transcripts have the potential to form dsRNA by base-pairing with sense transcripts.…”

Antisense Transcription in the Human Cytomegalovirus Transcriptome

“…Individual AS transcripts have been described for many herpesviruses, including the betaherpesviruses, (6,48,82), the gammaherpesviruses, (65,66,72), and especially the alphaherpesviruses, (8,9,13,16,21,25,26,42,49,50,53,68,84,88,89,91). In fact, Roizman and colleagues predicted that genes in AS orientation to known herpesvirus genes could be common (16).…”

Characterization of an Antisense Transcript Spanning the UL81-82 Locus of Human Cytomegalovirus

“…Transcripts in the antisense orientation to lytic cycle genes during latency are present in an impressive collection of herpesviruses (5,6,12,(30)(31)(32)46). It is possible that UL82 and UL81-82ast transcripts are mutually exclusive.…”