Bidirectional transcription of the Epstein-Barr virus major internal repeat

In latently infected cell lines, the Epstein-Barr virus BamHI W fragment (major internal repeat) is transcribed in a rightward direction to yield exons common to several alternatively spliced messages which encode the six known viral nuclear antigens. A substantial steady-state population of very large (up to 20-kilobase) rightward transcripts is nuclear, much of it being polyadenylated. We report a rise in the levels of rightward transcripts hybridizing to BamHI-W sequences upon phorbol ester treatment of the clone-13 Burkitt's lymphoma cell line. We also report large (up to 15-kilobase) leftward transcripts hybridizing to BamHI-W sequences which occurred late in the viral lytic cycle in B95-8 and clone-13 cells. These leftward transcripts may antagonize the expression of the viral nuclear antigen messages by the formation of RNA duplexes.